Fix updating/creating remotes/p4/* heads from origin/p4/*

[git.git] / contrib / fast-import / git-p4.txt

diff --git a/contrib/fast-import/git-p4.txt b/contrib/fast-import/git-p4.txt
index 4f6a680f95f2c3f11a25bb0f0c795dab4bcc5419..c315158d8d7eb110b927c920f0fe348ff612054f 100644 (file)
--- a/contrib/fast-import/git-p4.txt
+++ b/contrib/fast-import/git-p4.txt
@@ -4,8 +4,8 @@ Usage
 =====
 
 git-p4 supports two main modes: Importing from Perforce to a Git repository is
-done using "git-p4 sync". Submitting changes from Git back to Perforce is
-done using "git-p4 submit".
+done using "git-p4 sync" or "git-p4 rebase". Submitting changes from Git back
+to Perforce is done using "git-p4 submit".
 
 Importing
 =========
@@ -20,9 +20,9 @@ or
 
 This will create an empty git repository in a subdirectory called "project" (or
 "myproject" with the second command), import the head revision from the
-specified perforce path into a git "p4" branch, create a master branch off it
-and check it out. If you want the entire history (not just the head revision) then
-you can simply append a "@all" to the depot path:
+specified perforce path into a git "p4" branch (remotes/p4 actually), create a
+master branch off it and check it out. If you want the entire history (not just
+the head revision) then you can simply append a "@all" to the depot path:
 
   git-p4 clone //depot/project/main@all myproject
 
@@ -49,10 +49,6 @@ a big import. This may take a while.
 Support for Perforce integrations is still work in progress. Don't bother
 trying it unless you want to hack on it :)
 
-For convenience there's also the git-p4 clone command that works similar to
-git-clone and combines the creation of the git repository with the the initial
-import and the branch setup
-
 Incremental Imports
 ===================
 
@@ -67,6 +63,18 @@ It is recommended to run 'git repack -a -d -f' from time to time when using
 incremental imports to optimally combine the individual git packs that each
 incremental import creates through the use of git-fast-import.
 
+
+A useful setup may be that you have a periodically updated git repository
+somewhere that contains a complete import of a Perforce project. That git
+repository can be used to clone the working repository from and one would
+import from Perforce directly after cloning using git-p4. If the connection to
+the Perforce server is slow and the working repository hasn't been synced for a
+while it may be desirable to fetch changes from the origin git repository using
+the efficient git protocol. git-p4 supports this setup by calling "git fetch origin"
+by default if there is an origin branch. You can disable this using
+
+  git config git-p4.syncFromOrigin false
+
 Updating
 ========
 
@@ -104,6 +112,13 @@ continue importing the remaining changes with
 After submitting you should sync your perforce import branch ("p4" or "origin")
 from Perforce using git-p4's sync command.
 
+If you have changes in your working directory that you haven't committed into
+git yet but that you want to commit to Perforce directly ("quick fixes") then
+you do not have to go through the intermediate step of creating a git commit
+first but you can just call
+
+  git-p4 submit --direct
+
 
 Example
 =======
@@ -125,3 +140,20 @@ Example
   git-p4 rebase
 
 
+Implementation Details...
+=========================
+
+* Changesets from Perforce are imported using git fast-import.
+* The import does not require anything from the Perforce client view as it just uses
+  "p4 print //depot/path/file#revision" to get the actual file contents.
+* Every imported changeset has a special [git-p4...] line at the
+  end of the log message that gives information about the corresponding
+  Perforce change number and is also used by git-p4 itself to find out
+  where to continue importing when doing incremental imports.
+  Basically when syncing it extracts the perforce change number of the
+  latest commit in the "p4" branch and uses "p4 changes //depot/path/...@changenum,#head"
+  to find out which changes need to be imported.
+* git-p4 submit uses "git rev-list" to pick the commits between the "p4" branch
+  and the current branch.
+  The commits themselves are applied using git diff/format-patch ... | git apply
+