X-Git-Url: https://git.tokkee.org/?a=blobdiff_plain;f=Documentation%2Fuser-manual.txt;h=1c49e6995b42e42f1aba4e7b24d073e50c3b5234;hb=3a81b9f571a6b7edd83b3d5f27c3c95d9b1c9d5c;hp=03736bbcd3ebfd5e1cbe6a006acb2b31411af527;hpb=0bce7a52f2b723bf6717be2951df7c0a49337592;p=git.git diff --git a/Documentation/user-manual.txt b/Documentation/user-manual.txt index 03736bbcd..1c49e6995 100644 --- a/Documentation/user-manual.txt +++ b/Documentation/user-manual.txt @@ -2,7 +2,7 @@ Git User's Manual _________________ This manual is designed to be readable by someone with basic unix -commandline skills, but no previous knowledge of git. +command-line skills, but no previous knowledge of git. Chapter 1 gives a brief overview of git commands, without any explanation; you may prefer to skip to chapter 2 on a first reading. @@ -288,21 +288,22 @@ collection of files. It stores the history as a compressed collection of interrelated snapshots (versions) of the project's contents. -A single git repository may contain multiple branches. Each branch -is a bookmark referencing a particular point in the project history. -The gitlink:git-branch[1] command shows you the list of branches: +A single git repository may contain multiple branches. It keeps track +of them by keeping a list of <> which reference the +latest version on each branch; the gitlink:git-branch[1] command shows +you the list of branch heads: ------------------------------------------------ $ git branch * master ------------------------------------------------ -A freshly cloned repository contains a single branch, named "master", -and the working directory contains the version of the project -referred to by the master branch. +A freshly cloned repository contains a single branch head, named +"master", and working directory is initialized to the state of +the project referred to by "master". -Most projects also use tags. Tags, like branches, are references -into the project's history, and can be listed using the +Most projects also use <>. Tags, like heads, are +references into the project's history, and can be listed using the gitlink:git-tag[1] command: ------------------------------------------------ @@ -320,9 +321,9 @@ 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. +while heads are expected to advance as development progresses. -Create a new branch pointing to one of these versions and check it +Create a new branch head pointing to one of these versions and check it out using gitlink:git-checkout[1]: ------------------------------------------------ @@ -346,10 +347,10 @@ the current branch to point at v2.6.17 instead, with $ git reset --hard v2.6.17 ------------------------------------------------ -Note that if the current branch was your only reference to a +Note that if the current branch head was your only reference to a particular point in history, then resetting that branch may leave you -with no way to find the history it used to point to; so use this -command carefully. +with no way to find the history it used to point to; so use this command +carefully. Understanding History: Commits ------------------------------ @@ -391,15 +392,20 @@ 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 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). +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). Since the object name is computed as a hash over the +contents of the commit, you are guaranteed that the commit can never change +without its name also changing. + +In fact, in <> we shall see that everything stored in git +history, including file data and directory contents, is stored in an object +with a name that is a hash of its contents. Understanding history: commits, parents, and reachability ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -432,11 +438,14 @@ We will sometimes represent git history using diagrams like the one below. Commits are shown as "o", and the links between them with lines drawn with - / and \. Time goes left to right: + +................................................ o--o--o <-- Branch A / o--o--o <-- master \ o--o--o <-- Branch B +................................................ If we need to talk about a particular commit, the character "o" may be replaced with another letter or number. @@ -444,17 +453,15 @@ be replaced with another letter or number. Understanding history: What is a branch? ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -Though we've been using the word "branch" to mean a kind of reference -to a particular commit, the word branch is also commonly used to -refer to the line of commits leading up to that point. In the -example above, git may think of the branch named "A" as just a -pointer to one particular commit, but we may refer informally to the -line of three commits leading up to that point as all being part of +When we need to be precise, we will use the word "branch" to mean a line +of development, and "branch head" (or just "head") to mean a reference +to the most recent commit on a branch. In the example above, the branch +head named "A" is a pointer to one particular commit, but we refer to +the line of three commits leading up to that point as all being part of "branch A". -If we need to make it clear that we're just talking about the most -recent commit on the branch, we may refer to that commit as the -"head" of the branch. +However, when no confusion will result, we often just use the term +"branch" both for branches and for branch heads. Manipulating branches --------------------- @@ -596,8 +603,8 @@ a new stanza: $ cat .git/config ... [remote "linux-nfs"] - url = git://linux-nfs.org/~bfields/git.git - fetch = +refs/heads/*:refs/remotes/linux-nfs-read/* + url = git://linux-nfs.org/pub/nfs-2.6.git + fetch = +refs/heads/*:refs/remotes/linux-nfs/* ... ------------------------------------------------- @@ -1128,17 +1135,9 @@ modified in two different ways in the remote branch and the local branch--then you are warned; the output may look something like this: ------------------------------------------------- -$ git pull . next -Trying really trivial in-index merge... -fatal: Merge requires file-level merging -Nope. -Merging HEAD with 77976da35a11db4580b80ae27e8d65caf5208086 -Merging: -15e2162 world -77976da goodbye -found 1 common ancestor(s): -d122ed4 initial -Auto-merging file.txt +$ git merge next + 100% (4/4) done +Auto-merged file.txt CONFLICT (content): Merge conflict in file.txt Automatic merge failed; fix conflicts and then commit the result. ------------------------------------------------- @@ -1163,18 +1162,46 @@ the working tree in a special state that gives you all the information you need to help resolve the merge. Files with conflicts are marked specially in the index, so until you -resolve the problem and update the index, git commit will fail: +resolve the problem and update the index, gitlink:git-commit[1] will +fail: ------------------------------------------------- $ git commit file.txt: needs merge ------------------------------------------------- -Also, git status will list those files as "unmerged". +Also, gitlink:git-status[1] will list those files as "unmerged", and the +files with conflicts will have conflict markers added, like this: + +------------------------------------------------- +<<<<<<< HEAD:file.txt +Hello world +======= +Goodbye +>>>>>>> 77976da35a11db4580b80ae27e8d65caf5208086:file.txt +------------------------------------------------- + +All you need to do is edit the files to resolve the conflicts, and then + +------------------------------------------------- +$ git add file.txt +$ git commit +------------------------------------------------- + +Note that the commit message will already be filled in for you with +some information about the merge. Normally you can just use this +default message unchanged, but you may add additional commentary of +your own if desired. + +The above is all you need to know to resolve a simple merge. But git +also provides more information to help resolve conflicts: + +Getting conflict-resolution help during a merge +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ All of the changes that git was able to merge automatically are already added to the index file, so gitlink:git-diff[1] shows only -the conflicts. Also, it uses a somewhat unusual syntax: +the conflicts. It uses an unusual syntax: ------------------------------------------------- $ git diff @@ -1195,14 +1222,32 @@ conflict will have two parents instead of the usual one: one parent will be HEAD, the tip of the current branch; the other will be the tip of the other branch, which is stored temporarily in MERGE_HEAD. -The diff above shows the differences between the working-tree version -of file.txt and two previous version: one version from HEAD, and one -from MERGE_HEAD. So instead of preceding each line by a single "+" -or "-", it now uses two columns: the first column is used for -differences between the first parent and the working directory copy, -and the second for differences between the second parent and the -working directory copy. Thus after resolving the conflict in the -obvious way, the diff will look like: +During the merge, the index holds three versions of each file. Each of +these three "file stages" represents a different version of the file: + +------------------------------------------------- +$ git show :1:file.txt # the file in a common ancestor of both branches +$ git show :2:file.txt # the version from HEAD, but including any + # nonconflicting changes from MERGE_HEAD +$ git show :3:file.txt # the version from MERGE_HEAD, but including any + # nonconflicting changes from HEAD. +------------------------------------------------- + +Since the stage 2 and stage 3 versions have already been updated with +nonconflicting changes, the only remaining differences between them are +the important ones; thus gitlink:git-diff[1] can use the information in +the index to show only those conflicts. + +The diff above shows the differences between the working-tree version of +file.txt and the stage 2 and stage 3 versions. So instead of preceding +each line by a single "+" or "-", it now uses two columns: the first +column is used for differences between the first parent and the working +directory copy, and the second for differences between the second parent +and the working directory copy. (See the "COMBINED DIFF FORMAT" section +of gitlink:git-diff-files[1] for a details of the format.) + +After resolving the conflict in the obvious way (but before updating the +index), the diff will look like: ------------------------------------------------- $ git diff @@ -1220,26 +1265,37 @@ This shows that our resolved version deleted "Hello world" from the first parent, deleted "Goodbye" from the second parent, and added "Goodbye world", which was previously absent from both. -The gitlink:git-log[1] command also provides special help for merges: +Some special diff options allow diffing the working directory against +any of these stages: + +------------------------------------------------- +$ git diff -1 file.txt # diff against stage 1 +$ git diff --base file.txt # same as the above +$ git diff -2 file.txt # diff against stage 2 +$ git diff --ours file.txt # same as the above +$ git diff -3 file.txt # diff against stage 3 +$ git diff --theirs file.txt # same as the above. +------------------------------------------------- + +The gitlink:git-log[1] and gitk[1] commands also provide special help +for merges: ------------------------------------------------- $ git log --merge +$ gitk --merge ------------------------------------------------- -This will list all commits which exist only on HEAD or on MERGE_HEAD, -and which touch an unmerged file. +These will display all commits which exist only on HEAD or on +MERGE_HEAD, and which touch an unmerged file. -We can now add the resolved version to the index and commit: +Each time you resolve the conflicts in a file and update the index: ------------------------------------------------- $ git add file.txt -$ git commit ------------------------------------------------- -Note that the commit message will already be filled in for you with -some information about the merge. Normally you can just use this -default message unchanged, but you may add additional commentary of -your own if desired. +the different stages of that file will be "collapsed", after which +git-diff will (by default) no longer show diffs for that file. [[undoing-a-merge]] undoing a merge @@ -1255,7 +1311,7 @@ $ git reset --hard HEAD Or, if you've already commited the merge that you want to throw away, ------------------------------------------------- -$ git reset --hard HEAD^ +$ git reset --hard ORIG_HEAD ------------------------------------------------- However, this last command can be dangerous in some cases--never @@ -1328,6 +1384,7 @@ 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]] Fixing a mistake by editing history ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -1376,7 +1433,7 @@ modifying the working directory, you can do that with gitlink:git-show[1]: ------------------------------------------------- -$ git show HEAD^ path/to/file +$ git show HEAD^:path/to/file ------------------------------------------------- which will display the given version of the file. @@ -1479,7 +1536,7 @@ 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 +it contained. 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": @@ -1505,7 +1562,7 @@ 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.) +and complex commit history that was dropped.) If you decide you want the history back, you can always create a new reference pointing to it, for example, a new branch: @@ -1561,7 +1618,7 @@ repository that you pulled from. (But note that no such commit will be created in the case of a <>; instead, your branch will just be -updated to point to the latest commit from the upstream branch). +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 @@ -1638,9 +1695,9 @@ updates with git pull>>". If you and maintainer both have accounts on the same machine, then then you can just pull changes from each other's repositories -directly; note that all of the command (gitlink:git-clone[1], -git-fetch[1], git-pull[1], etc.) which accept a URL as an argument -will also accept a local file patch; so, for example, you can +directly; note that all of the commands (gitlink:git-clone[1], +git-fetch[1], git-pull[1], etc.) that accept a URL as an argument +will also accept a local directory name; so, for example, you can use ------------------------------------------------- @@ -1832,7 +1889,7 @@ 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. +may find that 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. @@ -1858,11 +1915,8 @@ 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 that you create a branch "mywork" on a remote-tracking branch +"origin", and create some commits on top of it: ------------------------------------------------- $ git checkout -b mywork origin @@ -1876,25 +1930,29 @@ $ git commit You have performed no merges into mywork, so it is just a simple linear sequence of patches on top of "origin": - +................................................ o--o--o <-- origin \ o--o--o <-- mywork +................................................ Some more interesting work has been done in the upstream project, and "origin" has advanced: +................................................ o--o--O--o--o--o <-- origin \ a--b--c <-- mywork +................................................ At this point, you could use "pull" to merge your changes back in; the result would create a new merge commit, like this: - +................................................ o--o--O--o--o--o <-- origin \ \ a--b--c--m <-- mywork +................................................ However, if you prefer to keep the history in mywork a simple series of commits without any merges, you may instead choose to use @@ -1911,9 +1969,11 @@ 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; after fixing conflicts, use "git @@ -1933,6 +1993,51 @@ return mywork to the state it had before you started the rebase: $ git rebase --abort ------------------------------------------------- +Modifying a single commit +------------------------- + +We saw in <> that you can replace the +most recent commit using + +------------------------------------------------- +$ 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. + +You can also use a combination of this and gitlink:git-rebase[1] to edit +commits further back in your history. First, tag the problematic commit with + +------------------------------------------------- +$ git tag bad mywork~5 +------------------------------------------------- + +(Either gitk or git-log may be useful for finding the commit.) + +Then check out a new branch at that commit, edit it, and rebase the rest of +the series on top of it: + +------------------------------------------------- +$ git checkout -b TMP bad +$ # make changes here and update the index +$ git commit --amend +$ git rebase --onto TMP bad mywork +------------------------------------------------- + +When you're done, you'll be left with mywork checked out, with the top patches +on mywork reapplied on top of the modified commit you created in TMP. You can +then clean up with + +------------------------------------------------- +$ git branch -d TMP +$ git tag -d bad +------------------------------------------------- + +Note that the immutable nature of git history means that you haven't really +"modified" existing commits; instead, you have replaced the old commits with +new commits having new object names. + Reordering or selecting from a patch series ------------------------------------------- @@ -1966,7 +2071,7 @@ Other tools ----------- 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 +purpose of maintaining a patch series. These are outside of the scope of this manual. Problems with rewriting history @@ -1976,24 +2081,30 @@ 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 @@ -2054,9 +2165,11 @@ 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 @@ -2064,11 +2177,11 @@ 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. @@ -2088,7 +2201,7 @@ 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 +Note the addition of the "+" sign. Be aware that commits that the old version of example/master pointed at may be lost, as we saw in the previous section. @@ -2096,7 +2209,7 @@ 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 +repository that you originally cloned from. This information is stored in git configuration variables, which you can see using gitlink:git-config[1]: @@ -2158,6 +2271,7 @@ See gitlink:git-config[1] for more details on the configuration options mentioned above. +[[git-internals]] Git internals ============= @@ -2407,7 +2521,7 @@ 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 +Those are the ONLY three 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 @@ -2898,9 +3012,6 @@ 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 -===================== - include::glossary.txt[] Notes and todo list for this manual @@ -2939,11 +3050,6 @@ provides. 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. - 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?