X-Git-Url: https://git.tokkee.org/?a=blobdiff_plain;f=Documentation%2Fuser-manual.txt;h=03736bbcd3ebfd5e1cbe6a006acb2b31411af527;hb=50cfde14531a5b354bbc3a070fe39c1ee86e2915;hp=a2fd5d27561a0893ab2ab95626729c1e34504256;hpb=e9c0390a9251714f4f4b54b4e3dddb2e65d18fa8;p=git.git diff --git a/Documentation/user-manual.txt b/Documentation/user-manual.txt index a2fd5d275..03736bbcd 100644 --- a/Documentation/user-manual.txt +++ b/Documentation/user-manual.txt @@ -4,12 +4,15 @@ _________________ This manual is designed to be readable by someone with basic unix commandline skills, but no previous knowledge of git. -Chapters 1 and 2 explain how to fetch and study a project using git--the -tools you'd need to build and test a particular version of a software -project, to search for regressions, and so on. +Chapter 1 gives a brief overview of git commands, without any +explanation; you may prefer to skip to chapter 2 on a first reading. -Chapter 3 explains how to do development with git and share your progress -with others. +Chapters 2 and 3 explain how to fetch and study a project using +git--the tools you'd need to build and test a particular version of a +software project, to search for regressions, and so on. + +Chapter 4 explains how to do development with git, and chapter 5 how +to share that development with others. Further chapters cover more specialized topics. @@ -20,6 +23,230 @@ pages. For a command such as "git clone", just use $ man git-clone ------------------------------------------------ +Git Quick Start +=============== + +This is a quick summary of the major commands; the following chapters +will explain how these work in more detail. + +Creating a new repository +------------------------- + +From a tarball: + +----------------------------------------------- +$ tar xzf project.tar.gz +$ cd project +$ git init +Initialized empty Git repository in .git/ +$ git add . +$ git commit +----------------------------------------------- + +From a remote repository: + +----------------------------------------------- +$ git clone git://example.com/pub/project.git +$ cd project +----------------------------------------------- + +Managing branches +----------------- + +----------------------------------------------- +$ git branch # list all branches in this repo +$ git checkout test # switch working directory to branch "test" +$ git branch new # create branch "new" starting at current HEAD +$ git branch -d new # delete branch "new" +----------------------------------------------- + +Instead of basing new branch on current HEAD (the default), use: + +----------------------------------------------- +$ git branch new test # branch named "test" +$ git branch new v2.6.15 # tag named v2.6.15 +$ git branch new HEAD^ # commit before the most recent +$ git branch new HEAD^^ # commit before that +$ git branch new test~10 # ten commits before tip of branch "test" +----------------------------------------------- + +Create and switch to a new branch at the same time: + +----------------------------------------------- +$ git checkout -b new v2.6.15 +----------------------------------------------- + +Update and examine branches from the repository you cloned from: + +----------------------------------------------- +$ git fetch # update +$ git branch -r # list + origin/master + origin/next + ... +$ git branch checkout -b masterwork origin/master +----------------------------------------------- + +Fetch a branch from a different repository, and give it a new +name in your repository: + +----------------------------------------------- +$ git fetch git://example.com/project.git theirbranch:mybranch +$ git fetch git://example.com/project.git v2.6.15:mybranch +----------------------------------------------- + +Keep a list of repositories you work with regularly: + +----------------------------------------------- +$ git remote add example git://example.com/project.git +$ git remote # list remote repositories +example +origin +$ git remote show example # get details +* remote example + URL: git://example.com/project.git + Tracked remote branches + master next ... +$ git fetch example # update branches from example +$ git branch -r # list all remote branches +----------------------------------------------- + + +Exploring history +----------------- + +----------------------------------------------- +$ gitk # visualize and browse history +$ git log # list all commits +$ git log src/ # ...modifying src/ +$ git log v2.6.15..v2.6.16 # ...in v2.6.16, not in v2.6.15 +$ git log master..test # ...in branch test, not in branch master +$ git log test..master # ...in branch master, but not in test +$ git log test...master # ...in one branch, not in both +$ git log -S'foo()' # ...where difference contain "foo()" +$ git log --since="2 weeks ago" +$ git log -p # show patches as well +$ git show # most recent commit +$ git diff v2.6.15..v2.6.16 # diff between two tagged versions +$ git diff v2.6.15..HEAD # diff with current head +$ git grep "foo()" # search working directory for "foo()" +$ git grep v2.6.15 "foo()" # search old tree for "foo()" +$ git show v2.6.15:a.txt # look at old version of a.txt +----------------------------------------------- + +Search for regressions: + +----------------------------------------------- +$ git bisect start +$ git bisect bad # current version is bad +$ git bisect good v2.6.13-rc2 # last known good revision +Bisecting: 675 revisions left to test after this + # test here, then: +$ git bisect good # if this revision is good, or +$ git bisect bad # if this revision is bad. + # repeat until done. +----------------------------------------------- + +Making changes +-------------- + +Make sure git knows who to blame: + +------------------------------------------------ +$ cat >~/.gitconfig <<\EOF +[user] +name = Your Name Comes Here +email = you@yourdomain.example.com +EOF +------------------------------------------------ + +Select file contents to include in the next commit, then make the +commit: + +----------------------------------------------- +$ git add a.txt # updated file +$ git add b.txt # new file +$ git rm c.txt # old file +$ git commit +----------------------------------------------- + +Or, prepare and create the commit in one step: + +----------------------------------------------- +$ git commit d.txt # use latest content only of d.txt +$ git commit -a # use latest content of all tracked files +----------------------------------------------- + +Merging +------- + +----------------------------------------------- +$ git merge test # merge branch "test" into the current branch +$ git pull git://example.com/project.git master + # fetch and merge in remote branch +$ git pull . test # equivalent to git merge test +----------------------------------------------- + +Sharing your changes +-------------------- + +Importing or exporting patches: + +----------------------------------------------- +$ git format-patch origin..HEAD # format a patch for each commit + # in HEAD but not in origin +$ git-am mbox # import patches from the mailbox "mbox" +----------------------------------------------- + +Fetch a branch in a different git repository, then merge into the +current branch: + +----------------------------------------------- +$ git pull git://example.com/project.git theirbranch +----------------------------------------------- + +Store the fetched branch into a local branch before merging into the +current branch: + +----------------------------------------------- +$ git pull git://example.com/project.git theirbranch:mybranch +----------------------------------------------- + +After creating commits on a local branch, update the remote +branch with your commits: + +----------------------------------------------- +$ git push ssh://example.com/project.git mybranch:theirbranch +----------------------------------------------- + +When remote and local branch are both named "test": + +----------------------------------------------- +$ git push ssh://example.com/project.git test +----------------------------------------------- + +Shortcut version for a frequently used remote repository: + +----------------------------------------------- +$ git remote add example ssh://example.com/project.git +$ git push example test +----------------------------------------------- + +Repository maintenance +---------------------- + +Check for corruption: + +----------------------------------------------- +$ git fsck +----------------------------------------------- + +Recompress, remove unused cruft: + +----------------------------------------------- +$ git gc +----------------------------------------------- + Repositories and Branches ========================= @@ -50,7 +277,7 @@ directory, you will see that it contains a copy of the project files, together with a special top-level directory named ".git", which contains all the information about the history of the project. -In the following, examples will be taken from one of the two +In most of the following, examples will be taken from one of the two repositories above. How to check out a different version of a project @@ -92,6 +319,9 @@ v2.6.13 ... ------------------------------------------------ +Tags are expected to always point at the same version of a project, +while branches are expected to advance as development progresses. + Create a new branch pointing to one of these versions and check it out using gitlink:git-checkout[1]: @@ -161,13 +391,15 @@ index 8be626f..d7aac9d 100644 As you can see, a commit shows who made the latest change, what they did, and why. -Every commit has a 20-digit id, sometimes called the "SHA1 id", shown -on the first line of the "git show" output. You can usually refer to -a commit by a shorter name, such as a tag or a branch name, but this -longer id can also be useful. In particular, it is a globally unique -name for this commit: so if you tell somebody else the SHA1 id (for -example in email), then you are guaranteed they will see the same -commit in their repository that you do in yours. +Every commit has a 40-hexdigit id, sometimes called the "object name" +or the "SHA1 id", shown on the first line of the "git show" output. +You can usually refer to a commit by a shorter name, such as a tag or a +branch name, but this longer name can also be useful. Most +importantly, it is a globally unique name for this commit: so if you +tell somebody else the object name (for example in email), then you are +guaranteed that name will refer to the same commit in their repository +that it does in yours (assuming their repository has that commit at +all). Understanding history: commits, parents, and reachability ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -193,8 +425,8 @@ if commit X is an ancestor of commit Y. Equivalently, you could say that Y is a descendent of X, or that there is a chain of parents leading from commit Y to commit X. -Undestanding history: History diagrams -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Understanding history: History diagrams +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ We will sometimes represent git history using diagrams like the one below. Commits are shown as "o", and the links between them with @@ -291,41 +523,33 @@ Note that the name "origin" is just the name that git uses by default to refer to the repository that you cloned from. [[how-git-stores-references]] -How git stores references -------------------------- +Naming branches, tags, and other references +------------------------------------------- Branches, remote-tracking branches, and tags are all references to -commits. Git stores these references in the ".git" directory. Most -of them are stored in .git/refs/: - - - branches are stored in .git/refs/heads - - tags are stored in .git/refs/tags - - remote-tracking branches for "origin" are stored in - .git/refs/remotes/origin/ +commits. All references are named with a slash-separated path name +starting with "refs"; the names we've been using so far are actually +shorthand: -If you look at one of these files you will see that they usually -contain just the SHA1 id of a commit: + - The branch "test" is short for "refs/heads/test". + - The tag "v2.6.18" is short for "refs/tags/v2.6.18". + - "origin/master" is short for "refs/remotes/origin/master". ------------------------------------------------- -$ ls .git/refs/heads/ -master -$ cat .git/refs/heads/master -c0f982dcf188d55db9d932a39d4ea7becaa55fed ------------------------------------------------- +The full name is occasionally useful if, for example, there ever +exists a tag and a branch with the same name. -You can refer to a reference by its path relative to the .git -directory. However, we've seen above that git will also accept -shorter names; for example, "master" is an acceptable shortcut for -"refs/heads/master", and "origin/master" is a shortcut for -"refs/remotes/origin/master". +As another useful shortcut, if the repository "origin" posesses only +a single branch, you can refer to that branch as just "origin". -As another useful shortcut, you can also refer to the "HEAD" of -"origin" (or any other remote), using just the name of the remote. +More generally, if you have defined a remote repository named +"example", you can refer to the branch in that repository as +"example". And for a repository with multiple branches, this will +refer to the branch designated as the "HEAD" branch. For the complete list of paths which git checks for references, and -how it decides which to choose when there are multiple references -with the same name, see the "SPECIFYING REVISIONS" section of -gitlink:git-rev-parse[1]. +the order it uses to decide which to choose when there are multiple +references with the same shorthand name, see the "SPECIFYING +REVISIONS" section of gitlink:git-rev-parse[1]. [[Updating-a-repository-with-git-fetch]] Updating a repository with git fetch @@ -340,149 +564,47 @@ remote-tracking branches to the latest version found in her repository. It will not touch any of your own branches--not even the "master" branch that was created for you on clone. -Fetching individual branches ----------------------------- - -You can also choose to update just one branch at a time: - -------------------------------------------------- -$ git fetch origin todo:refs/remotes/origin/todo -------------------------------------------------- - -The first argument, "origin", just tells git to fetch from the -repository you originally cloned from. The second argument tells git -to fetch the branch named "todo" from the remote repository, and to -store it locally under the name refs/remotes/origin/todo; as we saw -above, remote-tracking branches are stored under -refs/remotes//. - -You can also fetch branches from other repositories; so - -------------------------------------------------- -$ git fetch git://example.com/proj.git master:refs/remotes/example/master -------------------------------------------------- - -will create a new reference named "refs/remotes/example/master" and -store in it the branch named "master" from the repository at the -given URL. If you already have a branch named -"refs/remotes/example/master", it will attempt to "fast-forward" to -the commit given by example.com's master branch. So next we explain -what a fast-forward is: - -[[fast-forwards]] -Understanding git history: fast-forwards ----------------------------------------- - -In the previous example, when updating an existing branch, "git -fetch" checks to make sure that the most recent commit on the remote -branch is a descendant of the most recent commit on your copy of the -branch before updating your copy of the branch to point at the new -commit. Git calls this process a "fast forward". - -A fast forward looks something like this: - - o--o--o--o <-- old head of the branch - \ - o--o--o <-- new head of the branch - - -In some cases it is possible that the new head will *not* actually be -a descendant of the old head. For example, the developer may have -realized she made a serious mistake, and decided to backtrack, -resulting in a situation like: - - o--o--o--o--a--b <-- old head of the branch - \ - o--o--o <-- new head of the branch - - - -In this case, "git fetch" will fail, and print out a warning. - -In that case, you can still force git to update to the new head, as -described in the following section. However, note that in the -situation above this may mean losing the commits labeled "a" and "b", -unless you've already created a reference of your own pointing to -them. - -Forcing git fetch to do non-fast-forward updates ------------------------------------------------- - -If git fetch fails because the new head of a branch is not a -descendant of the old head, you may force the update with: - -------------------------------------------------- -$ git fetch git://example.com/proj.git +master:refs/remotes/example/master -------------------------------------------------- - -Note the addition of the "+" sign. Be aware that commits which the -old version of example/master pointed at may be lost, as we saw in -the previous section. - -Configuring remote branches ---------------------------- - -We saw above that "origin" is just a shortcut to refer to the -repository which you originally cloned from. This information is -stored in git configuration variables, which you can see using -gitlink:git-repo-config[1]: - -------------------------------------------------- -$ git-repo-config -l -core.repositoryformatversion=0 -core.filemode=true -core.logallrefupdates=true -remote.origin.url=git://git.kernel.org/pub/scm/git/git.git -remote.origin.fetch=+refs/heads/*:refs/remotes/origin/* -branch.master.remote=origin -branch.master.merge=refs/heads/master -------------------------------------------------- - -If there are other repositories that you also use frequently, you can -create similar configuration options to save typing; for example, -after - -------------------------------------------------- -$ git repo-config remote.example.url=git://example.com/proj.git -------------------------------------------------- +Fetching branches from other repositories +----------------------------------------- -then the following two commands will do the same thing: +You can also track branches from repositories other than the one you +cloned from, using gitlink:git-remote[1]: ------------------------------------------------- -$ git fetch git://example.com/proj.git master:refs/remotes/example/master -$ git fetch example master:refs/remotes/example/master +$ git remote add linux-nfs git://linux-nfs.org/pub/nfs-2.6.git +$ git fetch +* refs/remotes/linux-nfs/master: storing branch 'master' ... + commit: bf81b46 ------------------------------------------------- -Even better, if you add one more option: +New remote-tracking branches will be stored under the shorthand name +that you gave "git remote add", in this case linux-nfs: ------------------------------------------------- -$ git repo-config remote.example.fetch=master:refs/remotes/example/master +$ git branch -r +linux-nfs/master +origin/master ------------------------------------------------- -then the following commands will all do the same thing: - -------------------------------------------------- -$ git fetch git://example.com/proj.git master:ref/remotes/example/master -$ git fetch example master:ref/remotes/example/master -$ git fetch example example/master -$ git fetch example -------------------------------------------------- +If you run "git fetch " later, the tracking branches for the +named will be updated. -You can also add a "+" to force the update each time: +If you examine the file .git/config, you will see that git has added +a new stanza: ------------------------------------------------- -$ git repo-config +master:ref/remotes/example/master +$ cat .git/config +... +[remote "linux-nfs"] + url = git://linux-nfs.org/~bfields/git.git + fetch = +refs/heads/*:refs/remotes/linux-nfs-read/* +... ------------------------------------------------- -Don't do this unless you're sure you won't mind "git fetch" possibly -throwing away commits on mybranch. - -Also note that all of the above configuration can be performed by -directly editing the file .git/config instead of using -gitlink:git-repo-config[1]. - -See gitlink:git-repo-config[1] for more details on the configuration -options mentioned above. +This is what causes git to track the remote's branches; you may modify +or delete these configuration options by editing .git/config with a +text editor. (See the "CONFIGURATION FILE" section of +gitlink:git-config[1] for details.) Exploring git history ===================== @@ -495,7 +617,7 @@ the relationships between these snapshots. Git provides extremely flexible and fast tools for exploring the history of a project. -We start with one specialized tool which is useful for finding the +We start with one specialized tool that is useful for finding the commit that introduced a bug into a project. How to use bisect to find a regression @@ -570,7 +692,7 @@ Naming commits We have seen several ways of naming commits already: - - 20-digit SHA1 id + - 40-hexdigit object name - branch name: refers to the commit at the head of the given branch - tag name: refers to the commit pointed to by the given tag @@ -578,12 +700,12 @@ We have seen several ways of naming commits already: <>). - HEAD: refers to the head of the current branch -There are many more; see the "SPECIFYING REVISION" section of the -gitlink:git-rev-list[1] man page for the complete list of ways to +There are many more; see the "SPECIFYING REVISIONS" section of the +gitlink:git-rev-parse[1] man page for the complete list of ways to name revisions. Some examples: ------------------------------------------------- -$ git show fb47ddb2 # the first few characters of the SHA1 id +$ git show fb47ddb2 # the first few characters of the object name # are usually enough to specify it uniquely $ git show HEAD^ # the parent of the HEAD commit $ git show HEAD^^ # the grandparent @@ -620,6 +742,15 @@ When we discuss merges we'll also see the special name MERGE_HEAD, which refers to the other branch that we're merging in to the current branch. +The gitlink:git-rev-parse[1] command is a low-level command that is +occasionally useful for translating some name for a commit to the object +name for that commit: + +------------------------------------------------- +$ git rev-parse origin +e05db0fd4f31dde7005f075a84f96b360d05984b +------------------------------------------------- + Creating tags ------------- @@ -675,7 +806,7 @@ display options. Note that git log starts with the most recent commit and works backwards through the parents; however, since git history can contain -multiple independant lines of development, the particular order that +multiple independent lines of development, the particular order that commits are listed in may be somewhat arbitrary. Generating diffs @@ -714,6 +845,126 @@ $ git show v2.5:fs/locks.c Before the colon may be anything that names a commit, and after it may be any path to a file tracked by git. +Examples +-------- + +Check whether two branches point at the same history +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Suppose you want to check whether two branches point at the same point +in history. + +------------------------------------------------- +$ git diff origin..master +------------------------------------------------- + +will tell you whether the contents of the project are the same at the +two branches; in theory, however, it's possible that the same project +contents could have been arrived at by two different historical +routes. You could compare the object names: + +------------------------------------------------- +$ git rev-list origin +e05db0fd4f31dde7005f075a84f96b360d05984b +$ git rev-list master +e05db0fd4f31dde7005f075a84f96b360d05984b +------------------------------------------------- + +Or you could recall that the ... operator selects all commits +contained reachable from either one reference or the other but not +both: so + +------------------------------------------------- +$ git log origin...master +------------------------------------------------- + +will return no commits when the two branches are equal. + +Find first tagged version including a given fix +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Suppose you know that the commit e05db0fd fixed a certain problem. +You'd like to find the earliest tagged release that contains that +fix. + +Of course, there may be more than one answer--if the history branched +after commit e05db0fd, then there could be multiple "earliest" tagged +releases. + +You could just visually inspect the commits since e05db0fd: + +------------------------------------------------- +$ gitk e05db0fd.. +------------------------------------------------- + +Or you can use gitlink:git-name-rev[1], which will give the commit a +name based on any tag it finds pointing to one of the commit's +descendants: + +------------------------------------------------- +$ git name-rev e05db0fd +e05db0fd tags/v1.5.0-rc1^0~23 +------------------------------------------------- + +The gitlink:git-describe[1] command does the opposite, naming the +revision using a tag on which the given commit is based: + +------------------------------------------------- +$ git describe e05db0fd +v1.5.0-rc0-ge05db0f +------------------------------------------------- + +but that may sometimes help you guess which tags might come after the +given commit. + +If you just want to verify whether a given tagged version contains a +given commit, you could use gitlink:git-merge-base[1]: + +------------------------------------------------- +$ git merge-base e05db0fd v1.5.0-rc1 +e05db0fd4f31dde7005f075a84f96b360d05984b +------------------------------------------------- + +The merge-base command finds a common ancestor of the given commits, +and always returns one or the other in the case where one is a +descendant of the other; so the above output shows that e05db0fd +actually is an ancestor of v1.5.0-rc1. + +Alternatively, note that + +------------------------------------------------- +$ git log v1.5.0-rc1..e05db0fd +------------------------------------------------- + +will produce empty output if and only if v1.5.0-rc1 includes e05db0fd, +because it outputs only commits that are not reachable from v1.5.0-rc1. + +As yet another alternative, the gitlink:git-show-branch[1] command lists +the commits reachable from its arguments with a display on the left-hand +side that indicates which arguments that commit is reachable from. So, +you can run something like + +------------------------------------------------- +$ git show-branch e05db0fd v1.5.0-rc0 v1.5.0-rc1 v1.5.0-rc2 +! [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if +available + ! [v1.5.0-rc0] GIT v1.5.0 preview + ! [v1.5.0-rc1] GIT v1.5.0-rc1 + ! [v1.5.0-rc2] GIT v1.5.0-rc2 +... +------------------------------------------------- + +then search for a line that looks like + +------------------------------------------------- ++ ++ [e05db0fd] Fix warnings in sha1_file.c - use C99 printf format if +available +------------------------------------------------- + +Which shows that e05db0fd is reachable from itself, from v1.5.0-rc1, and +from v1.5.0-rc2, but not from v1.5.0-rc0. + + Developing with git =================== @@ -731,6 +982,9 @@ $ cat >~/.gitconfig <<\EOF EOF ------------------------------------------------ +(See the "CONFIGURATION FILE" section of gitlink:git-config[1] for +details on the configuration file.) + Creating a new repository ------------------------- @@ -740,7 +994,7 @@ Creating a new repository from scratch is very easy: ------------------------------------------------- $ mkdir project $ cd project -$ git init-db +$ git init ------------------------------------------------- If you have some initial content (say, a tarball): @@ -748,7 +1002,7 @@ If you have some initial content (say, a tarball): ------------------------------------------------- $ tar -xzvf project.tar.gz $ cd project -$ git init-db +$ git init $ git add . # include everything below ./ in the first commit: $ git commit ------------------------------------------------- @@ -770,9 +1024,10 @@ times as you want: in order to keep track of what you want committed at step 3, git maintains a snapshot of the tree's contents in a special staging area called "the index." -By default, the content of the index is identical to that of the -HEAD. The command "git diff --cached" shows the difference between -HEAD and the index, so you should no output from that command. +At the beginning, the content of the index will be identical to +that of the HEAD. The command "git diff --cached", which shows +the difference between the HEAD and the index, should therefore +produce no output at that point. Modifying the index is easy: @@ -788,8 +1043,7 @@ To add the contents of a new file to the index, use $ git add path/to/file ------------------------------------------------- -To remove a file from the index that you've removed from the working -tree, +To remove a file from the index and from the working tree, ------------------------------------------------- $ git rm path/to/file @@ -821,7 +1075,7 @@ $ git commit ------------------------------------------------- and git will prompt you for a commit message and then create the new -commmit. Check to make sure it looks like what you expected with +commit. Check to make sure it looks like what you expected with ------------------------------------------------- $ git show @@ -1024,30 +1278,249 @@ already contained in the other--then git just performs a moved forward to point at the head of the merged-in branch, without any new commits being created. -Ensuring good performance -------------------------- - -On large repositories, git depends on compression to keep the history -information from taking up to much space on disk or in memory. +Fixing mistakes +--------------- -This compression is not performed automatically. Therefore you -should occasionally run +If you've messed up the working tree, but haven't yet committed your +mistake, you can return the entire working tree to the last committed +state with + +------------------------------------------------- +$ git reset --hard HEAD +------------------------------------------------- + +If you make a commit that you later wish you hadn't, there are two +fundamentally different ways to fix the problem: + + 1. You can create a new commit that undoes whatever was done + by the previous commit. This is the correct thing if your + mistake has already been made public. + + 2. You can go back and modify the old commit. You should + never do this if you have already made the history public; + git does not normally expect the "history" of a project to + change, and cannot correctly perform repeated merges from + a branch that has had its history changed. + +Fixing a mistake with a new commit +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +Creating a new commit that reverts an earlier change is very easy; +just pass the gitlink:git-revert[1] command a reference to the bad +commit; for example, to revert the most recent commit: + +------------------------------------------------- +$ git revert HEAD +------------------------------------------------- + +This will create a new commit which undoes the change in HEAD. You +will be given a chance to edit the commit message for the new commit. + +You can also revert an earlier change, for example, the next-to-last: + +------------------------------------------------- +$ git revert HEAD^ +------------------------------------------------- + +In this case git will attempt to undo the old change while leaving +intact any changes made since then. If more recent changes overlap +with the changes to be reverted, then you will be asked to fix +conflicts manually, just as in the case of <>. + +Fixing a mistake by editing history +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +If the problematic commit is the most recent commit, and you have not +yet made that commit public, then you may just +<>. + +Alternatively, you +can edit the working directory and update the index to fix your +mistake, just as if you were going to <>, then run + +------------------------------------------------- +$ git commit --amend +------------------------------------------------- + +which will replace the old commit by a new commit incorporating your +changes, giving you a chance to edit the old commit message first. + +Again, you should never do this to a commit that may already have +been merged into another branch; use gitlink:git-revert[1] instead in +that case. + +It is also possible to edit commits further back in the history, but +this is an advanced topic to be left for +<>. + +Checking out an old version of a file +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +In the process of undoing a previous bad change, you may find it +useful to check out an older version of a particular file using +gitlink:git-checkout[1]. We've used git checkout before to switch +branches, but it has quite different behavior if it is given a path +name: the command + +------------------------------------------------- +$ git checkout HEAD^ path/to/file +------------------------------------------------- + +replaces path/to/file by the contents it had in the commit HEAD^, and +also updates the index to match. It does not change branches. + +If you just want to look at an old version of the file, without +modifying the working directory, you can do that with +gitlink:git-show[1]: + +------------------------------------------------- +$ git show HEAD^ path/to/file +------------------------------------------------- + +which will display the given version of the file. + +Ensuring good performance +------------------------- + +On large repositories, git depends on compression to keep the history +information from taking up to much space on disk or in memory. + +This compression is not performed automatically. Therefore you +should occasionally run gitlink:git-gc[1]: ------------------------------------------------- $ git gc ------------------------------------------------- -to recompress the archive and to prune any commits which are no -longer referred to anywhere. This can be very time-consuming, and -you should not modify the repository while it is working, so you -should run it while you are not working. +to recompress the archive. This can be very time-consuming, so +you may prefer to run git-gc when you are not doing other work. + +Ensuring reliability +-------------------- + +Checking the repository for corruption +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +The gitlink:git-fsck[1] command runs a number of self-consistency checks +on the repository, and reports on any problems. This may take some +time. The most common warning by far is about "dangling" objects: + +------------------------------------------------- +$ git fsck +dangling commit 7281251ddd2a61e38657c827739c57015671a6b3 +dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63 +dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5 +dangling blob 218761f9d90712d37a9c5e36f406f92202db07eb +dangling commit bf093535a34a4d35731aa2bd90fe6b176302f14f +dangling commit 8e4bec7f2ddaa268bef999853c25755452100f8e +dangling tree d50bb86186bf27b681d25af89d3b5b68382e4085 +dangling tree b24c2473f1fd3d91352a624795be026d64c8841f +... +------------------------------------------------- + +Dangling objects are objects that are harmless, but also unnecessary; +you can remove them at any time with gitlink:git-prune[1] or the --prune +option to gitlink:git-gc[1]: + +------------------------------------------------- +$ git gc --prune +------------------------------------------------- + +This may be time-consuming. Unlike most other git operations (including +git-gc when run without any options), it is not safe to prune while +other git operations are in progress in the same repository. + +For more about dangling objects, see <>. + + +Recovering lost changes +~~~~~~~~~~~~~~~~~~~~~~~ + +Reflogs +^^^^^^^ + +Say you modify a branch with gitlink:git-reset[1] --hard, and then +realize that the branch was the only reference you had to that point in +history. + +Fortunately, git also keeps a log, called a "reflog", of all the +previous values of each branch. So in this case you can still find the +old history using, for example, + +------------------------------------------------- +$ git log master@{1} +------------------------------------------------- + +This lists the commits reachable from the previous version of the head. +This syntax can be used to with any git command that accepts a commit, +not just with git log. Some other examples: + +------------------------------------------------- +$ git show master@{2} # See where the branch pointed 2, +$ git show master@{3} # 3, ... changes ago. +$ gitk master@{yesterday} # See where it pointed yesterday, +$ gitk master@{"1 week ago"} # ... or last week +------------------------------------------------- + +The reflogs are kept by default for 30 days, after which they may be +pruned. See gitlink:git-reflog[1] and gitlink:git-gc[1] to learn +how to control this pruning, and see the "SPECIFYING REVISIONS" +section of gitlink:git-rev-parse[1] for details. + +Note that the reflog history is very different from normal git history. +While normal history is shared by every repository that works on the +same project, the reflog history is not shared: it tells you only about +how the branches in your local repository have changed over time. + +Examining dangling objects +^^^^^^^^^^^^^^^^^^^^^^^^^^ + +In some situations the reflog may not be able to save you. For +example, suppose you delete a branch, then realize you need the history +it pointed you. The reflog is also deleted; however, if you have not +yet pruned the repository, then you may still be able to find +the lost commits; run git-fsck and watch for output that mentions +"dangling commits": + +------------------------------------------------- +$ git fsck +dangling commit 7281251ddd2a61e38657c827739c57015671a6b3 +dangling commit 2706a059f258c6b245f298dc4ff2ccd30ec21a63 +dangling commit 13472b7c4b80851a1bc551779171dcb03655e9b5 +... +------------------------------------------------- + +You can examine +one of those dangling commits with, for example, + +------------------------------------------------ +$ gitk 7281251ddd --not --all +------------------------------------------------ + +which does what it sounds like: it says that you want to see the commit +history that is described by the dangling commit(s), but not the +history that is described by all your existing branches and tags. Thus +you get exactly the history reachable from that commit that is lost. +(And notice that it might not be just one commit: we only report the +"tip of the line" as being dangling, but there might be a whole deep +and complex commit history that was gotten dropped.) + +If you decide you want the history back, you can always create a new +reference pointing to it, for example, a new branch: + +------------------------------------------------ +$ git branch recovered-branch 7281251ddd +------------------------------------------------ + Sharing development with others -------------------------------- +=============================== [[getting-updates-with-git-pull]] Getting updates with git pull -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +----------------------------- After you clone a repository and make a few changes of your own, you may wish to check the original repository for updates and merge them @@ -1079,7 +1552,7 @@ $ git pull ------------------------------------------------- See the descriptions of the branch..remote and -branch..merge options in gitlink:git-repo-config[1] to learn +branch..merge options in gitlink:git-config[1] to learn how to control these defaults depending on the current branch. In addition to saving you keystrokes, "git pull" also helps you by @@ -1090,8 +1563,8 @@ repository that you pulled from. <>; instead, your branch will just be updated to point to the latest commit from the upstream branch). -The git-pull command can also be given "." as the "remote" repository, in -which case it just merges in a branch from the current repository; so +The git-pull command can also be given "." as the "remote" repository, +in which case it just merges in a branch from the current repository; so the commands ------------------------------------------------- @@ -1102,15 +1575,15 @@ $ git merge branch are roughly equivalent. The former is actually very commonly used. Submitting patches to a project -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +------------------------------- If you just have a few changes, the simplest way to submit them may just be to send them as patches in email: -First, use gitlink:git-format-patches[1]; for example: +First, use gitlink:git-format-patch[1]; for example: ------------------------------------------------- -$ git format-patches origin +$ git format-patch origin ------------------------------------------------- will produce a numbered series of files in the current directory, one @@ -1123,7 +1596,7 @@ Consult the mailing list for your project first to determine how they prefer such patches be handled. Importing patches to a project -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +------------------------------ Git also provides a tool called gitlink:git-am[1] (am stands for "apply mailbox"), for importing such an emailed series of patches. @@ -1131,14 +1604,17 @@ Just save all of the patch-containing messages, in order, into a single mailbox file, say "patches.mbox", then run ------------------------------------------------- -$ git am patches.mbox +$ git am -3 patches.mbox ------------------------------------------------- Git will apply each patch in order; if any conflicts are found, it will stop, and you can fix the conflicts as described in -"<>". Once the index is updated -with the results of the conflict resolution, instead of creating a -new commit, just run +"<>". (The "-3" option tells +git to perform a merge; if you would prefer it just to abort and +leave your tree and index untouched, you may omit that option.) + +Once the index is updated with the results of the conflict +resolution, instead of creating a new commit, just run ------------------------------------------------- $ git am --resolved @@ -1153,7 +1629,7 @@ taken from the message containing each patch. [[setting-up-a-public-repository]] Setting up a public repository -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +------------------------------ Another way to submit changes to a project is to simply tell the maintainer of that project to pull from your repository, exactly as @@ -1219,7 +1695,7 @@ created public repository: [[exporting-via-http]] Exporting a git repository via http -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +----------------------------------- The git protocol gives better performance and reliability, but on a host with a web server set up, http exports may be simpler to set up. @@ -1253,7 +1729,7 @@ allows pushing over http.) [[exporting-via-git]] Exporting a git repository via the git protocol -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +----------------------------------------------- This is the preferred method. @@ -1262,7 +1738,7 @@ instructions. (See especially the examples section.) [[pushing-changes-to-a-public-repository]] Pushing changes to a public repository -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +-------------------------------------- Note that the two techniques outline above (exporting via <> or <>) allow other @@ -1311,11 +1787,11 @@ $ git push public-repo master ------------------------------------------------- See the explanations of the remote..url, branch..remote, -and remote..push options in gitlink:git-repo-config[1] for +and remote..push options in gitlink:git-config[1] for details. Setting up a shared repository -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +------------------------------ Another way to collaborate is by using a model similar to that commonly used in CVS, where several developers with special rights @@ -1323,165 +1799,70 @@ all push to and pull from a single shared repository. See link:cvs-migration.txt[git for CVS users] for instructions on how to set this up. -Fixing mistakes ---------------- - -If you've messed up the working tree, but haven't yet committed your -mistake, you can return the entire working tree to the last committed -state with +Allow web browsing of a repository +---------------------------------- -------------------------------------------------- -$ git reset --hard HEAD -------------------------------------------------- +The gitweb cgi script provides users an easy way to browse your +project's files and history without having to install git; see the file +gitweb/README in the git source tree for instructions on setting it up. -If you make a commit that you later wish you hadn't, there are two -fundamentally different ways to fix the problem: +Examples +-------- - 1. You can create a new commit that undoes whatever was done - by the previous commit. This is the correct thing if your - mistake has already been made public. +TODO: topic branches, typical roles as in everyday.txt, ? - 2. You can go back and modify the old commit. You should - never do this if you have already made the history public; - git does not normally expect the "history" of a project to - change, and cannot correctly perform repeated merges from - a branch that has had its history changed. -Fixing a mistake with a new commit -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +[[cleaning-up-history]] +Rewriting history and maintaining patch series +============================================== -Creating a new commit that reverts an earlier change is very easy; -just pass the gitlink:git-revert[1] command a reference to the bad -commit; for example, to revert the most recent commit: +Normally commits are only added to a project, never taken away or +replaced. Git is designed with this assumption, and violating it will +cause git's merge machinery (for example) to do the wrong thing. -------------------------------------------------- -$ git revert HEAD -------------------------------------------------- +However, there is a situation in which it can be useful to violate this +assumption. -This will create a new commit which undoes the change in HEAD. You -will be given a chance to edit the commit message for the new commit. +Creating the perfect patch series +--------------------------------- -You can also revert an earlier change, for example, the next-to-last: +Suppose you are a contributor to a large project, and you want to add a +complicated feature, and to present it to the other developers in a way +that makes it easy for them to read your changes, verify that they are +correct, and understand why you made each change. -------------------------------------------------- -$ git revert HEAD^ -------------------------------------------------- +If you present all of your changes as a single patch (or commit), they +may find it is too much to digest all at once. -In this case git will attempt to undo the old change while leaving -intact any changes made since then. If more recent changes overlap -with the changes to be reverted, then you will be asked to fix -conflicts manually, just as in the case of <>. +If you present them with the entire history of your work, complete with +mistakes, corrections, and dead ends, they may be overwhelmed. -Fixing a mistake by editing history -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +So the ideal is usually to produce a series of patches such that: -If the problematic commit is the most recent commit, and you have not -yet made that commit public, then you may just -<>. + 1. Each patch can be applied in order. -Alternatively, you -can edit the working directory and update the index to fix your -mistake, just as if you were going to <>, then run + 2. Each patch includes a single logical change, together with a + message explaining the change. -------------------------------------------------- -$ git commit --amend -------------------------------------------------- + 3. No patch introduces a regression: after applying any initial + part of the series, the resulting project still compiles and + works, and has no bugs that it didn't have before. -which will replace the old commit by a new commit incorporating your -changes, giving you a chance to edit the old commit message first. + 4. The complete series produces the same end result as your own + (probably much messier!) development process did. -Again, you should never do this to a commit that may already have -been merged into another branch; use gitlink:git-revert[1] instead in -that case. +We will introduce some tools that can help you do this, explain how to +use them, and then explain some of the problems that can arise because +you are rewriting history. -It is also possible to edit commits further back in the history, but -this is an advanced topic to be left for -<>. +Keeping a patch series up to date using git-rebase +-------------------------------------------------- -Checking out an old version of a file -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Suppose you have a series of commits in a branch "mywork", which +originally branched off from "origin". -In the process of undoing a previous bad change, you may find it -useful to check out an older version of a particular file using -gitlink:git-checkout[1]. We've used git checkout before to switch -branches, but it has quite different behavior if it is given a path -name: the command - -------------------------------------------------- -$ git checkout HEAD^ path/to/file -------------------------------------------------- - -replaces path/to/file by the contents it had in the commit HEAD^, and -also updates the index to match. It does not change branches. - -If you just want to look at an old version of the file, without -modifying the working directory, you can do that with -gitlink:git-show[1]: - -------------------------------------------------- -$ git show HEAD^ path/to/file -------------------------------------------------- - -which will display the given version of the file. - -Working with other version control systems -========================================== - -TODO: CVS, Subversion, series-of-release-tarballs, ? - -[[cleaning-up-history]] -Rewriting history and maintaining patch series -============================================== - -Normally commits are only added to a project, never taken away or -replaced. Git is designed with this assumption, and violating it will -cause git's merge machinery (for example) to do the wrong thing. - -However, there is a situation in which it can be useful to violate this -assumption. - -Creating the perfect patch series ---------------------------------- - -Suppose you are a contributor to a large project, and you want to add a -complicated feature, and to present it to the other developers in a way -that makes it easy for them to read your changes, verify that they are -correct, and understand why you made each change. - -If you present all of your changes as a single patch (or commit), they may -find it is too much to digest all at once. - -If you present them with the entire history of your work, complete with -mistakes, corrections, and dead ends, they may be overwhelmed. - -So the ideal is usually to produce a series of patches such that: - - 1. Each patch can be applied in order. - - 2. Each patch includes a single logical change, together with a - message explaining the change. - - 3. No patch introduces a regression: after applying any initial - part of the series, the resulting project still compiles and - works, and has no bugs that it didn't have before. - - 4. The complete series produces the same end result as your own - (probably much messier!) development process did. - -We will introduce some tools that can help you do this, explain how to use -them, and then explain some of the problems that can arise because you are -rewriting history. - -Keeping a patch series up to date using git-rebase --------------------------------------------------- - -Suppose you have a series of commits in a branch "mywork", which -originally branched off from "origin". - -Suppose you create a branch "mywork" on a remote-tracking branch "origin", -and created some commits on top of it: +Suppose you create a branch "mywork" on a remote-tracking branch +"origin", and created some commits on top of it: ------------------------------------------------- $ git checkout -b mywork origin @@ -1524,21 +1905,20 @@ $ git checkout mywork $ git rebase origin ------------------------------------------------- -This will remove each of your commits from mywork, temporarily saving them -as patches (in a directory named ".dotest"), update mywork to point at the -latest version of origin, then apply each of the saved patches to the new -mywork. The result will look like: +This will remove each of your commits from mywork, temporarily saving +them as patches (in a directory named ".dotest"), update mywork to +point at the latest version of origin, then apply each of the saved +patches to the new mywork. The result will look like: o--o--O--o--o--o <-- origin \ a'--b'--c' <-- mywork -In the process, it may discover conflicts. In that case it will stop and -allow you to fix the conflicts as described in -"<>". Once the index is updated with -the results of the conflict resolution, instead of creating a new commit, -just run +In the process, it may discover conflicts. In that case it will stop +and allow you to fix the conflicts; after fixing conflicts, use "git +add" to update the index with those contents, and then, instead of +running git-commit, just run ------------------------------------------------- $ git rebase --continue @@ -1556,36 +1936,967 @@ $ git rebase --abort Reordering or selecting from a patch series ------------------------------------------- -Given one existing commit, the gitlink:git-cherry-pick[1] command allows -you to apply the change introduced by that commit and create a new commit -that records it. +Given one existing commit, the gitlink:git-cherry-pick[1] command +allows you to apply the change introduced by that commit and create a +new commit that records it. So, for example, if "mywork" points to a +series of patches on top of "origin", you might do something like: -This can be useful for modifying a patch series. +------------------------------------------------- +$ git checkout -b mywork-new origin +$ gitk origin..mywork & +------------------------------------------------- + +And browse through the list of patches in the mywork branch using gitk, +applying them (possibly in a different order) to mywork-new using +cherry-pick, and possibly modifying them as you go using commit +--amend. + +Another technique is to use git-format-patch to create a series of +patches, then reset the state to before the patches: + +------------------------------------------------- +$ git format-patch origin +$ git reset --hard origin +------------------------------------------------- -TODO: elaborate +Then modify, reorder, or eliminate patches as preferred before applying +them again with gitlink:git-am[1]. Other tools ----------- -There are numerous other tools, such as stgit, which exist for the purpose -of maintianing a patch series. These are out of the scope of this manual. +There are numerous other tools, such as stgit, which exist for the +purpose of maintaining a patch series. These are out of the scope of +this manual. Problems with rewriting history ------------------------------- -The primary problem with rewriting the history of a branch has to do with -merging. +The primary problem with rewriting the history of a branch has to do +with merging. Suppose somebody fetches your branch and merges it into +their branch, with a result something like this: + + o--o--O--o--o--o <-- origin + \ \ + t--t--t--m <-- their branch: + +Then suppose you modify the last three commits: + + o--o--o <-- new head of origin + / + o--o--O--o--o--o <-- old head of origin + +If we examined all this history together in one repository, it will +look like: + + o--o--o <-- new head of origin + / + o--o--O--o--o--o <-- old head of origin + \ \ + t--t--t--m <-- their branch: + +Git has no way of knowing that the new head is an updated version of +the old head; it treats this situation exactly the same as it would if +two developers had independently done the work on the old and new heads +in parallel. At this point, if someone attempts to merge the new head +in to their branch, git will attempt to merge together the two (old and +new) lines of development, instead of trying to replace the old by the +new. The results are likely to be unexpected. + +You may still choose to publish branches whose history is rewritten, +and it may be useful for others to be able to fetch those branches in +order to examine or test them, but they should not attempt to pull such +branches into their own work. + +For true distributed development that supports proper merging, +published branches should never be rewritten. + +Advanced branch management +========================== + +Fetching individual branches +---------------------------- + +Instead of using gitlink:git-remote[1], you can also choose just +to update one branch at a time, and to store it locally under an +arbitrary name: + +------------------------------------------------- +$ git fetch origin todo:my-todo-work +------------------------------------------------- + +The first argument, "origin", just tells git to fetch from the +repository you originally cloned from. The second argument tells git +to fetch the branch named "todo" from the remote repository, and to +store it locally under the name refs/heads/my-todo-work. + +You can also fetch branches from other repositories; so + +------------------------------------------------- +$ git fetch git://example.com/proj.git master:example-master +------------------------------------------------- + +will create a new branch named "example-master" and store in it the +branch named "master" from the repository at the given URL. If you +already have a branch named example-master, it will attempt to +"fast-forward" to the commit given by example.com's master branch. So +next we explain what a fast-forward is: + +[[fast-forwards]] +Understanding git history: fast-forwards +---------------------------------------- + +In the previous example, when updating an existing branch, "git +fetch" checks to make sure that the most recent commit on the remote +branch is a descendant of the most recent commit on your copy of the +branch before updating your copy of the branch to point at the new +commit. Git calls this process a "fast forward". + +A fast forward looks something like this: + + o--o--o--o <-- old head of the branch + \ + o--o--o <-- new head of the branch + + +In some cases it is possible that the new head will *not* actually be +a descendant of the old head. For example, the developer may have +realized she made a serious mistake, and decided to backtrack, +resulting in a situation like: + + o--o--o--o--a--b <-- old head of the branch + \ + o--o--o <-- new head of the branch + + + +In this case, "git fetch" will fail, and print out a warning. + +In that case, you can still force git to update to the new head, as +described in the following section. However, note that in the +situation above this may mean losing the commits labeled "a" and "b", +unless you've already created a reference of your own pointing to +them. + +Forcing git fetch to do non-fast-forward updates +------------------------------------------------ + +If git fetch fails because the new head of a branch is not a +descendant of the old head, you may force the update with: + +------------------------------------------------- +$ git fetch git://example.com/proj.git +master:refs/remotes/example/master +------------------------------------------------- + +Note the addition of the "+" sign. Be aware that commits which the +old version of example/master pointed at may be lost, as we saw in +the previous section. + +Configuring remote branches +--------------------------- + +We saw above that "origin" is just a shortcut to refer to the +repository which you originally cloned from. This information is +stored in git configuration variables, which you can see using +gitlink:git-config[1]: + +------------------------------------------------- +$ git config -l +core.repositoryformatversion=0 +core.filemode=true +core.logallrefupdates=true +remote.origin.url=git://git.kernel.org/pub/scm/git/git.git +remote.origin.fetch=+refs/heads/*:refs/remotes/origin/* +branch.master.remote=origin +branch.master.merge=refs/heads/master +------------------------------------------------- + +If there are other repositories that you also use frequently, you can +create similar configuration options to save typing; for example, +after + +------------------------------------------------- +$ git config remote.example.url git://example.com/proj.git +------------------------------------------------- + +then the following two commands will do the same thing: + +------------------------------------------------- +$ git fetch git://example.com/proj.git master:refs/remotes/example/master +$ git fetch example master:refs/remotes/example/master +------------------------------------------------- + +Even better, if you add one more option: + +------------------------------------------------- +$ git config remote.example.fetch master:refs/remotes/example/master +------------------------------------------------- + +then the following commands will all do the same thing: + +------------------------------------------------- +$ git fetch git://example.com/proj.git master:ref/remotes/example/master +$ git fetch example master:ref/remotes/example/master +$ git fetch example example/master +$ git fetch example +------------------------------------------------- + +You can also add a "+" to force the update each time: + +------------------------------------------------- +$ git config remote.example.fetch +master:ref/remotes/example/master +------------------------------------------------- + +Don't do this unless you're sure you won't mind "git fetch" possibly +throwing away commits on mybranch. + +Also note that all of the above configuration can be performed by +directly editing the file .git/config instead of using +gitlink:git-config[1]. -TODO: elaborate +See gitlink:git-config[1] for more details on the configuration +options mentioned above. Git internals ============= -Architectural overview +There are two object abstractions: the "object database", and the +"current directory cache" aka "index". + +The Object Database +------------------- + +The object database is literally just a content-addressable collection +of objects. All objects are named by their content, which is +approximated by the SHA1 hash of the object itself. Objects may refer +to other objects (by referencing their SHA1 hash), and so you can +build up a hierarchy of objects. + +All objects have a statically determined "type" aka "tag", which is +determined at object creation time, and which identifies the format of +the object (i.e. how it is used, and how it can refer to other +objects). There are currently four different object types: "blob", +"tree", "commit" and "tag". + +A "blob" object cannot refer to any other object, and is, like the type +implies, a pure storage object containing some user data. It is used to +actually store the file data, i.e. a blob object is associated with some +particular version of some file. + +A "tree" object is an object that ties one or more "blob" objects into a +directory structure. In addition, a tree object can refer to other tree +objects, thus creating a directory hierarchy. + +A "commit" object ties such directory hierarchies together into +a DAG of revisions - each "commit" is associated with exactly one tree +(the directory hierarchy at the time of the commit). In addition, a +"commit" refers to one or more "parent" commit objects that describe the +history of how we arrived at that directory hierarchy. + +As a special case, a commit object with no parents is called the "root" +object, and is the point of an initial project commit. Each project +must have at least one root, and while you can tie several different +root objects together into one project by creating a commit object which +has two or more separate roots as its ultimate parents, that's probably +just going to confuse people. So aim for the notion of "one root object +per project", even if git itself does not enforce that. + +A "tag" object symbolically identifies and can be used to sign other +objects. It contains the identifier and type of another object, a +symbolic name (of course!) and, optionally, a signature. + +Regardless of object type, all objects share the following +characteristics: they are all deflated with zlib, and have a header +that not only specifies their type, but also provides size information +about the data in the object. It's worth noting that the SHA1 hash +that is used to name the object is the hash of the original data +plus this header, so `sha1sum` 'file' does not match the object name +for 'file'. +(Historical note: in the dawn of the age of git the hash +was the sha1 of the 'compressed' object.) + +As a result, the general consistency of an object can always be tested +independently of the contents or the type of the object: all objects can +be validated by verifying that (a) their hashes match the content of the +file and (b) the object successfully inflates to a stream of bytes that +forms a sequence of + + + + . + +The structured objects can further have their structure and +connectivity to other objects verified. This is generally done with +the `git-fsck` program, which generates a full dependency graph +of all objects, and verifies their internal consistency (in addition +to just verifying their superficial consistency through the hash). + +The object types in some more detail: + +Blob Object +----------- + +A "blob" object is nothing but a binary blob of data, and doesn't +refer to anything else. There is no signature or any other +verification of the data, so while the object is consistent (it 'is' +indexed by its sha1 hash, so the data itself is certainly correct), it +has absolutely no other attributes. No name associations, no +permissions. It is purely a blob of data (i.e. normally "file +contents"). + +In particular, since the blob is entirely defined by its data, if two +files in a directory tree (or in multiple different versions of the +repository) have the same contents, they will share the same blob +object. The object is totally independent of its location in the +directory tree, and renaming a file does not change the object that +file is associated with in any way. + +A blob is typically created when gitlink:git-update-index[1] +is run, and its data can be accessed by gitlink:git-cat-file[1]. + +Tree Object +----------- + +The next hierarchical object type is the "tree" object. A tree object +is a list of mode/name/blob data, sorted by name. Alternatively, the +mode data may specify a directory mode, in which case instead of +naming a blob, that name is associated with another TREE object. + +Like the "blob" object, a tree object is uniquely determined by the +set contents, and so two separate but identical trees will always +share the exact same object. This is true at all levels, i.e. it's +true for a "leaf" tree (which does not refer to any other trees, only +blobs) as well as for a whole subdirectory. + +For that reason a "tree" object is just a pure data abstraction: it +has no history, no signatures, no verification of validity, except +that since the contents are again protected by the hash itself, we can +trust that the tree is immutable and its contents never change. + +So you can trust the contents of a tree to be valid, the same way you +can trust the contents of a blob, but you don't know where those +contents 'came' from. + +Side note on trees: since a "tree" object is a sorted list of +"filename+content", you can create a diff between two trees without +actually having to unpack two trees. Just ignore all common parts, +and your diff will look right. In other words, you can effectively +(and efficiently) tell the difference between any two random trees by +O(n) where "n" is the size of the difference, rather than the size of +the tree. + +Side note 2 on trees: since the name of a "blob" depends entirely and +exclusively on its contents (i.e. there are no names or permissions +involved), you can see trivial renames or permission changes by +noticing that the blob stayed the same. However, renames with data +changes need a smarter "diff" implementation. + +A tree is created with gitlink:git-write-tree[1] and +its data can be accessed by gitlink:git-ls-tree[1]. +Two trees can be compared with gitlink:git-diff-tree[1]. + +Commit Object +------------- + +The "commit" object is an object that introduces the notion of +history into the picture. In contrast to the other objects, it +doesn't just describe the physical state of a tree, it describes how +we got there, and why. + +A "commit" is defined by the tree-object that it results in, the +parent commits (zero, one or more) that led up to that point, and a +comment on what happened. Again, a commit is not trusted per se: +the contents are well-defined and "safe" due to the cryptographically +strong signatures at all levels, but there is no reason to believe +that the tree is "good" or that the merge information makes sense. +The parents do not have to actually have any relationship with the +result, for example. + +Note on commits: unlike real SCM's, commits do not contain +rename information or file mode change information. All of that is +implicit in the trees involved (the result tree, and the result trees +of the parents), and describing that makes no sense in this idiotic +file manager. + +A commit is created with gitlink:git-commit-tree[1] and +its data can be accessed by gitlink:git-cat-file[1]. + +Trust +----- + +An aside on the notion of "trust". Trust is really outside the scope +of "git", but it's worth noting a few things. First off, since +everything is hashed with SHA1, you 'can' trust that an object is +intact and has not been messed with by external sources. So the name +of an object uniquely identifies a known state - just not a state that +you may want to trust. + +Furthermore, since the SHA1 signature of a commit refers to the +SHA1 signatures of the tree it is associated with and the signatures +of the parent, a single named commit specifies uniquely a whole set +of history, with full contents. You can't later fake any step of the +way once you have the name of a commit. + +So to introduce some real trust in the system, the only thing you need +to do is to digitally sign just 'one' special note, which includes the +name of a top-level commit. Your digital signature shows others +that you trust that commit, and the immutability of the history of +commits tells others that they can trust the whole history. + +In other words, you can easily validate a whole archive by just +sending out a single email that tells the people the name (SHA1 hash) +of the top commit, and digitally sign that email using something +like GPG/PGP. + +To assist in this, git also provides the tag object... + +Tag Object +---------- + +Git provides the "tag" object to simplify creating, managing and +exchanging symbolic and signed tokens. The "tag" object at its +simplest simply symbolically identifies another object by containing +the sha1, type and symbolic name. + +However it can optionally contain additional signature information +(which git doesn't care about as long as there's less than 8k of +it). This can then be verified externally to git. + +Note that despite the tag features, "git" itself only handles content +integrity; the trust framework (and signature provision and +verification) has to come from outside. + +A tag is created with gitlink:git-mktag[1], +its data can be accessed by gitlink:git-cat-file[1], +and the signature can be verified by +gitlink:git-verify-tag[1]. + + +The "index" aka "Current Directory Cache" +----------------------------------------- + +The index is a simple binary file, which contains an efficient +representation of a virtual directory content at some random time. It +does so by a simple array that associates a set of names, dates, +permissions and content (aka "blob") objects together. The cache is +always kept ordered by name, and names are unique (with a few very +specific rules) at any point in time, but the cache has no long-term +meaning, and can be partially updated at any time. + +In particular, the index certainly does not need to be consistent with +the current directory contents (in fact, most operations will depend on +different ways to make the index 'not' be consistent with the directory +hierarchy), but it has three very important attributes: + +'(a) it can re-generate the full state it caches (not just the +directory structure: it contains pointers to the "blob" objects so +that it can regenerate the data too)' + +As a special case, there is a clear and unambiguous one-way mapping +from a current directory cache to a "tree object", which can be +efficiently created from just the current directory cache without +actually looking at any other data. So a directory cache at any one +time uniquely specifies one and only one "tree" object (but has +additional data to make it easy to match up that tree object with what +has happened in the directory) + +'(b) it has efficient methods for finding inconsistencies between that +cached state ("tree object waiting to be instantiated") and the +current state.' + +'(c) it can additionally efficiently represent information about merge +conflicts between different tree objects, allowing each pathname to be +associated with sufficient information about the trees involved that +you can create a three-way merge between them.' + +Those are the three ONLY things that the directory cache does. It's a +cache, and the normal operation is to re-generate it completely from a +known tree object, or update/compare it with a live tree that is being +developed. If you blow the directory cache away entirely, you generally +haven't lost any information as long as you have the name of the tree +that it described. + +At the same time, the index is at the same time also the +staging area for creating new trees, and creating a new tree always +involves a controlled modification of the index file. In particular, +the index file can have the representation of an intermediate tree that +has not yet been instantiated. So the index can be thought of as a +write-back cache, which can contain dirty information that has not yet +been written back to the backing store. + + + +The Workflow +------------ + +Generally, all "git" operations work on the index file. Some operations +work *purely* on the index file (showing the current state of the +index), but most operations move data to and from the index file. Either +from the database or from the working directory. Thus there are four +main combinations: + +working directory -> index +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +You update the index with information from the working directory with +the gitlink:git-update-index[1] command. You +generally update the index information by just specifying the filename +you want to update, like so: + +------------------------------------------------- +$ git-update-index filename +------------------------------------------------- + +but to avoid common mistakes with filename globbing etc, the command +will not normally add totally new entries or remove old entries, +i.e. it will normally just update existing cache entries. + +To tell git that yes, you really do realize that certain files no +longer exist, or that new files should be added, you +should use the `--remove` and `--add` flags respectively. + +NOTE! A `--remove` flag does 'not' mean that subsequent filenames will +necessarily be removed: if the files still exist in your directory +structure, the index will be updated with their new status, not +removed. The only thing `--remove` means is that update-cache will be +considering a removed file to be a valid thing, and if the file really +does not exist any more, it will update the index accordingly. + +As a special case, you can also do `git-update-index --refresh`, which +will refresh the "stat" information of each index to match the current +stat information. It will 'not' update the object status itself, and +it will only update the fields that are used to quickly test whether +an object still matches its old backing store object. + +index -> object database +~~~~~~~~~~~~~~~~~~~~~~~~ + +You write your current index file to a "tree" object with the program + +------------------------------------------------- +$ git-write-tree +------------------------------------------------- + +that doesn't come with any options - it will just write out the +current index into the set of tree objects that describe that state, +and it will return the name of the resulting top-level tree. You can +use that tree to re-generate the index at any time by going in the +other direction: + +object database -> index +~~~~~~~~~~~~~~~~~~~~~~~~ + +You read a "tree" file from the object database, and use that to +populate (and overwrite - don't do this if your index contains any +unsaved state that you might want to restore later!) your current +index. Normal operation is just + +------------------------------------------------- +$ git-read-tree +------------------------------------------------- + +and your index file will now be equivalent to the tree that you saved +earlier. However, that is only your 'index' file: your working +directory contents have not been modified. + +index -> working directory +~~~~~~~~~~~~~~~~~~~~~~~~~~ + +You update your working directory from the index by "checking out" +files. This is not a very common operation, since normally you'd just +keep your files updated, and rather than write to your working +directory, you'd tell the index files about the changes in your +working directory (i.e. `git-update-index`). + +However, if you decide to jump to a new version, or check out somebody +else's version, or just restore a previous tree, you'd populate your +index file with read-tree, and then you need to check out the result +with + +------------------------------------------------- +$ git-checkout-index filename +------------------------------------------------- + +or, if you want to check out all of the index, use `-a`. + +NOTE! git-checkout-index normally refuses to overwrite old files, so +if you have an old version of the tree already checked out, you will +need to use the "-f" flag ('before' the "-a" flag or the filename) to +'force' the checkout. + + +Finally, there are a few odds and ends which are not purely moving +from one representation to the other: + +Tying it all together +~~~~~~~~~~~~~~~~~~~~~ + +To commit a tree you have instantiated with "git-write-tree", you'd +create a "commit" object that refers to that tree and the history +behind it - most notably the "parent" commits that preceded it in +history. + +Normally a "commit" has one parent: the previous state of the tree +before a certain change was made. However, sometimes it can have two +or more parent commits, in which case we call it a "merge", due to the +fact that such a commit brings together ("merges") two or more +previous states represented by other commits. + +In other words, while a "tree" represents a particular directory state +of a working directory, a "commit" represents that state in "time", +and explains how we got there. + +You create a commit object by giving it the tree that describes the +state at the time of the commit, and a list of parents: + +------------------------------------------------- +$ git-commit-tree -p [-p ..] +------------------------------------------------- + +and then giving the reason for the commit on stdin (either through +redirection from a pipe or file, or by just typing it at the tty). + +git-commit-tree will return the name of the object that represents +that commit, and you should save it away for later use. Normally, +you'd commit a new `HEAD` state, and while git doesn't care where you +save the note about that state, in practice we tend to just write the +result to the file pointed at by `.git/HEAD`, so that we can always see +what the last committed state was. + +Here is an ASCII art by Jon Loeliger that illustrates how +various pieces fit together. + +------------ + + commit-tree + commit obj + +----+ + | | + | | + V V + +-----------+ + | Object DB | + | Backing | + | Store | + +-----------+ + ^ + write-tree | | + tree obj | | + | | read-tree + | | tree obj + V + +-----------+ + | Index | + | "cache" | + +-----------+ + update-index ^ + blob obj | | + | | + checkout-index -u | | checkout-index + stat | | blob obj + V + +-----------+ + | Working | + | Directory | + +-----------+ + +------------ + + +Examining the data +------------------ + +You can examine the data represented in the object database and the +index with various helper tools. For every object, you can use +gitlink:git-cat-file[1] to examine details about the +object: + +------------------------------------------------- +$ git-cat-file -t +------------------------------------------------- + +shows the type of the object, and once you have the type (which is +usually implicit in where you find the object), you can use + +------------------------------------------------- +$ git-cat-file blob|tree|commit|tag +------------------------------------------------- + +to show its contents. NOTE! Trees have binary content, and as a result +there is a special helper for showing that content, called +`git-ls-tree`, which turns the binary content into a more easily +readable form. + +It's especially instructive to look at "commit" objects, since those +tend to be small and fairly self-explanatory. In particular, if you +follow the convention of having the top commit name in `.git/HEAD`, +you can do + +------------------------------------------------- +$ git-cat-file commit HEAD +------------------------------------------------- + +to see what the top commit was. + +Merging multiple trees ---------------------- -TODO: Sources, README, core-tutorial, tutorial-2.txt, technical/ +Git helps you do a three-way merge, which you can expand to n-way by +repeating the merge procedure arbitrary times until you finally +"commit" the state. The normal situation is that you'd only do one +three-way merge (two parents), and commit it, but if you like to, you +can do multiple parents in one go. + +To do a three-way merge, you need the two sets of "commit" objects +that you want to merge, use those to find the closest common parent (a +third "commit" object), and then use those commit objects to find the +state of the directory ("tree" object) at these points. + +To get the "base" for the merge, you first look up the common parent +of two commits with + +------------------------------------------------- +$ git-merge-base +------------------------------------------------- + +which will return you the commit they are both based on. You should +now look up the "tree" objects of those commits, which you can easily +do with (for example) + +------------------------------------------------- +$ git-cat-file commit | head -1 +------------------------------------------------- + +since the tree object information is always the first line in a commit +object. + +Once you know the three trees you are going to merge (the one "original" +tree, aka the common case, and the two "result" trees, aka the branches +you want to merge), you do a "merge" read into the index. This will +complain if it has to throw away your old index contents, so you should +make sure that you've committed those - in fact you would normally +always do a merge against your last commit (which should thus match what +you have in your current index anyway). + +To do the merge, do + +------------------------------------------------- +$ git-read-tree -m -u +------------------------------------------------- + +which will do all trivial merge operations for you directly in the +index file, and you can just write the result out with +`git-write-tree`. + + +Merging multiple trees, continued +--------------------------------- + +Sadly, many merges aren't trivial. If there are files that have +been added.moved or removed, or if both branches have modified the +same file, you will be left with an index tree that contains "merge +entries" in it. Such an index tree can 'NOT' be written out to a tree +object, and you will have to resolve any such merge clashes using +other tools before you can write out the result. + +You can examine such index state with `git-ls-files --unmerged` +command. An example: + +------------------------------------------------ +$ git-read-tree -m $orig HEAD $target +$ git-ls-files --unmerged +100644 263414f423d0e4d70dae8fe53fa34614ff3e2860 1 hello.c +100644 06fa6a24256dc7e560efa5687fa84b51f0263c3a 2 hello.c +100644 cc44c73eb783565da5831b4d820c962954019b69 3 hello.c +------------------------------------------------ + +Each line of the `git-ls-files --unmerged` output begins with +the blob mode bits, blob SHA1, 'stage number', and the +filename. The 'stage number' is git's way to say which tree it +came from: stage 1 corresponds to `$orig` tree, stage 2 `HEAD` +tree, and stage3 `$target` tree. + +Earlier we said that trivial merges are done inside +`git-read-tree -m`. For example, if the file did not change +from `$orig` to `HEAD` nor `$target`, or if the file changed +from `$orig` to `HEAD` and `$orig` to `$target` the same way, +obviously the final outcome is what is in `HEAD`. What the +above example shows is that file `hello.c` was changed from +`$orig` to `HEAD` and `$orig` to `$target` in a different way. +You could resolve this by running your favorite 3-way merge +program, e.g. `diff3` or `merge`, on the blob objects from +these three stages yourself, like this: + +------------------------------------------------ +$ git-cat-file blob 263414f... >hello.c~1 +$ git-cat-file blob 06fa6a2... >hello.c~2 +$ git-cat-file blob cc44c73... >hello.c~3 +$ merge hello.c~2 hello.c~1 hello.c~3 +------------------------------------------------ + +This would leave the merge result in `hello.c~2` file, along +with conflict markers if there are conflicts. After verifying +the merge result makes sense, you can tell git what the final +merge result for this file is by: + +------------------------------------------------- +$ mv -f hello.c~2 hello.c +$ git-update-index hello.c +------------------------------------------------- + +When a path is in unmerged state, running `git-update-index` for +that path tells git to mark the path resolved. + +The above is the description of a git merge at the lowest level, +to help you understand what conceptually happens under the hood. +In practice, nobody, not even git itself, uses three `git-cat-file` +for this. There is `git-merge-index` program that extracts the +stages to temporary files and calls a "merge" script on it: + +------------------------------------------------- +$ git-merge-index git-merge-one-file hello.c +------------------------------------------------- + +and that is what higher level `git merge -s resolve` is implemented with. + +How git stores objects efficiently: pack files +---------------------------------------------- + +We've seen how git stores each object in a file named after the +object's SHA1 hash. + +Unfortunately this system becomes inefficient once a project has a +lot of objects. Try this on an old project: + +------------------------------------------------ +$ git count-objects +6930 objects, 47620 kilobytes +------------------------------------------------ + +The first number is the number of objects which are kept in +individual files. The second is the amount of space taken up by +those "loose" objects. + +You can save space and make git faster by moving these loose objects in +to a "pack file", which stores a group of objects in an efficient +compressed format; the details of how pack files are formatted can be +found in link:technical/pack-format.txt[technical/pack-format.txt]. + +To put the loose objects into a pack, just run git repack: + +------------------------------------------------ +$ git repack +Generating pack... +Done counting 6020 objects. +Deltifying 6020 objects. + 100% (6020/6020) done +Writing 6020 objects. + 100% (6020/6020) done +Total 6020, written 6020 (delta 4070), reused 0 (delta 0) +Pack pack-3e54ad29d5b2e05838c75df582c65257b8d08e1c created. +------------------------------------------------ + +You can then run + +------------------------------------------------ +$ git prune +------------------------------------------------ + +to remove any of the "loose" objects that are now contained in the +pack. This will also remove any unreferenced objects (which may be +created when, for example, you use "git reset" to remove a commit). +You can verify that the loose objects are gone by looking at the +.git/objects directory or by running + +------------------------------------------------ +$ git count-objects +0 objects, 0 kilobytes +------------------------------------------------ + +Although the object files are gone, any commands that refer to those +objects will work exactly as they did before. + +The gitlink:git-gc[1] command performs packing, pruning, and more for +you, so is normally the only high-level command you need. + +[[dangling-objects]] +Dangling objects +---------------- + +The gitlink:git-fsck[1] command will sometimes complain about dangling +objects. They are not a problem. + +The most common cause of dangling objects is that you've rebased a +branch, or you have pulled from somebody else who rebased a branch--see +<>. In that case, the old head of the original +branch still exists, as does obviously everything it pointed to. The +branch pointer itself just doesn't, since you replaced it with another +one. + +There are also other situations too that cause dangling objects. For +example, a "dangling blob" may arise because you did a "git add" of a +file, but then, before you actually committed it and made it part of the +bigger picture, you changed something else in that file and committed +that *updated* thing - the old state that you added originally ends up +not being pointed to by any commit or tree, so it's now a dangling blob +object. + +Similarly, when the "recursive" merge strategy runs, and finds that +there are criss-cross merges and thus more than one merge base (which is +fairly unusual, but it does happen), it will generate one temporary +midway tree (or possibly even more, if you had lots of criss-crossing +merges and more than two merge bases) as a temporary internal merge +base, and again, those are real objects, but the end result will not end +up pointing to them, so they end up "dangling" in your repository. + +Generally, dangling objects aren't anything to worry about. They can +even be very useful: if you screw something up, the dangling objects can +be how you recover your old tree (say, you did a rebase, and realized +that you really didn't want to - you can look at what dangling objects +you have, and decide to reset your head to some old dangling state). + +For commits, the most useful thing to do with dangling objects tends to +be to do a simple + +------------------------------------------------ +$ gitk --not --all +------------------------------------------------ + +For blobs and trees, you can't do the same, but you can examine them. +You can just do + +------------------------------------------------ +$ git show +------------------------------------------------ + +to show what the contents of the blob were (or, for a tree, basically +what the "ls" for that directory was), and that may give you some idea +of what the operation was that left that dangling object. + +Usually, dangling blobs and trees aren't very interesting. They're +almost always the result of either being a half-way mergebase (the blob +will often even have the conflict markers from a merge in it, if you +have had conflicting merges that you fixed up by hand), or simply +because you interrupted a "git fetch" with ^C or something like that, +leaving _some_ of the new objects in the object database, but just +dangling and useless. + +Anyway, once you are sure that you're not interested in any dangling +state, you can just prune all unreachable objects: + +------------------------------------------------ +$ git prune +------------------------------------------------ + +and they'll be gone. But you should only run "git prune" on a quiescent +repository - it's kind of like doing a filesystem fsck recovery: you +don't want to do that while the filesystem is mounted. + +(The same is true of "git-fsck" itself, btw - but since +git-fsck never actually *changes* the repository, it just reports +on what it found, git-fsck itself is never "dangerous" to run. +Running it while somebody is actually changing the repository can cause +confusing and scary messages, but it won't actually do anything bad. In +contrast, running "git prune" while somebody is actively changing the +repository is a *BAD* idea). Glossary of git terms ===================== @@ -1598,56 +2909,53 @@ Notes and todo list for this manual This is a work in progress. The basic requirements: - - It must be readable in order, from beginning to end, by someone - intelligent with a basic grasp of the unix commandline, but - without any special knowledge of git. If necessary, any other - prerequisites should be specifically mentioned as they arise. - - Whenever possible, section headings should clearly describe the - task they explain how to do, in language that requires no more - knowledge than necessary: for example, "importing patches into a - project" rather than "the git-am command" - -Think about how to create a clear chapter dependency graph that will allow -people to get to important topics without necessarily reading everything -in between. + - It must be readable in order, from beginning to end, by + someone intelligent with a basic grasp of the unix + commandline, but without any special knowledge of git. If + necessary, any other prerequisites should be specifically + mentioned as they arise. + - Whenever possible, section headings should clearly describe + the task they explain how to do, in language that requires + no more knowledge than necessary: for example, "importing + patches into a project" rather than "the git-am command" + +Think about how to create a clear chapter dependency graph that will +allow people to get to important topics without necessarily reading +everything in between. + +Say something about .gitignore. Scan Documentation/ for other stuff left out; in particular: howto's - README some of technical/? hooks - etc. + list of commands in gitlink:git[1] Scan email archives for other stuff left out Scan man pages to see if any assume more background than this manual provides. -Mention of gitweb. - -Update git fetch discussion to use "git remote" setup. That will -make things simpler. Maybe wait till git remote is done. - -Can also simplify beginning by suggesting disconnected head instead -of temporary branch creation. +Simplify beginning by suggesting disconnected head instead of +temporary branch creation? Explain how to refer to file stages in the "how to resolve a merge" section: diff -1, -2, -3, --ours, --theirs :1:/path notation. The -"git ls-files --unmerged --stage" thing is sorta useful too, actually. And -note gitk --merge. Also what's easiest way to see common merge base? +"git ls-files --unmerged --stage" thing is sorta useful too, +actually. And note gitk --merge. -Add more good examples. Entire sections of just cookbook examples might be a -good idea; maybe make an "advanced examples" section a standard end-of-chapter -section? +Add more good examples. Entire sections of just cookbook examples +might be a good idea; maybe make an "advanced examples" section a +standard end-of-chapter section? Include cross-references to the glossary, where appropriate. -Update for detached-head. +Document shallow clones? See draft 1.5.0 release notes for some +documentation. + +Add a section on working with other version control systems, including +CVS, Subversion, and just imports of series of release tarballs. -Update for git-remote. Even if the command isn't there yet, I think we should -probably just document the repository configuration necessary to set it up, as -the default way to keep a repository up-to-date. +More details on gitweb? -To document: - reflogs, git reflog expire - shallow clones?? See draft 1.5.0 release notes for some documentation. +Write a chapter on using plumbing and writing scripts.