Merge subtrees together and split repository into subtrees
gitsubtree add -P <prefix> <commit> gitsubtree add -P <prefix> <repository> <ref> gitsubtree pull -P <prefix> <repository> <ref> gitsubtree push -P <prefix> <repository> <ref> gitsubtree merge -P <prefix> <commit> gitsubtree split -P <prefix> [OPTIONS] [<commit>]
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In order to keep your commit messages clean, we recommend that people split their commits between the subtrees and the main project as much as possible . That is, if you make a change that affects both the library and the main application, commit it in two pieces . That way, when you split the library commits out later, their descriptions will still make sense . But if this isn important to you, it not necessary . git subtree will simply leave out the non -library -related parts of the commit when it splits it out into the subproject later .
add Create the <prefix> subtree by importing its contents from the given <commit> or <repository> and remote <ref> . A new commit is created automatically, joining the imported project history with your own . With --squash ,imports only a single commit from the subproject, rather than its entire history .
merge Merge recent changes up to <commit> into the <prefix> subtree . As with normal gitmerge ,this doesn remove your own local changes; it just merges those changes into the latest <commit> . With --squash ,creates only one commit that contains all the changes, rather than merging in the entire history .
pull Exactly like merge ,but parallels gitpull in that it fetches the given ref from the specified remote repository .
push Does a split (see below) using the <prefix> supplied and then does a gitpush to push the result to the repository and ref . This can be used to push your subtree to different branches of the remote repository .
split Extract a new, synthetic project history from the history of the <prefix> subtree . The new history includes only the commits (including merges) that affected <prefix>, and each of those commits now has the contents of <prefix> at the root of the project instead of in a subdirectory . Thus, the newly created history is suitable for export as a separate git repository . After splitting successfully, a single commit id is printed to stdout . This corresponds to the HEAD of the newly created tree, which you can manipulate however you want . Repeated splits of exactly the same history are guaranteed to be identical (i .e . to produce the same commit ids) . Because of this, if you add new commits and then re -split, the new commits will be attached as commits on top of the history you generated last time, so gitmerge and friends will work as expected . Note that if you use --squash when you merge, you should usually not just --rejoin when you split .
-q, --quiet Suppress unnecessary output messages on stderr .
-d, --debug Produce even more unnecessary output messages on stderr .
-P <prefix>, --prefix=<prefix> Specify the path in the repository to the subtree you want to manipulate . This option is mandatory for all commands .
-m <message>, --message=<message> This option is only valid for add, merge and pull (unsure) . Specify <message> as the commit message for the merge commit .
--squash This option is only valid for add, merge, and pull commands .Instead of merging the entire history from the subtree project, produce only a single commit that contains all the differences you want to merge, and then merge that new commit into your project . Using this option helps to reduce log clutter . People rarely want to see every change that happened between v1 .0 and v1 .1 of the library they using, since none of the interim versions were ever included in their application . Using --squash also helps avoid problems when the same subproject is included multiple times in the same project, or is removed and then re -added . In such a case, it doesn make sense to combine the histories anyway, since it unclear which part of the history belongs to which subtree . Furthermore, with --squash ,you can switch back and forth between different versions of a subtree, rather than strictly forward . gitsubtree merge --squash always adjusts the subtree to match the exactly specified commit, even if getting to that commit would require undoing some changes that were added earlier . Whether or not you use --squash ,changes made in your local repository remain intact and can be later split and send upstream to the subproject .
--annotate=<annotation> This option is only valid for the split command .When generating synthetic history, add <annotation> as a prefix to each commit message . Since we creating new commits with the same commit message, but possibly different content, from the original commits, this can help to differentiate them and avoid confusion . Whenever you split, you need to use the same <annotation>, or else you don have a guarantee that the new re -created history will be identical to the old one . That will prevent merging from working correctly . git subtree tries to make it work anyway, particularly if you use --rejoin, but it may not always be effective .
-b <branch>, --branch=<branch> This option is only valid for the split command . After generating the synthetic history, create a new branch called <branch> that contains the new history . This is suitable for immediate pushing upstream . <branch> must not already exist .
--ignore -joins This option is only valid for the split command . If you use --rejoin ,git subtree attempts to optimize its history reconstruction to generate only the new commits since the last --rejoin . --ignore -join disables this behaviour, forcing it to regenerate the entire history . In a large project, this can take a long time .
--onto=<onto> This option is only valid for the split command . If your subtree was originally imported using something other than git subtree, its history may not match what git subtree is expecting . In that case, you can specify the commit id <onto> that corresponds to the first revision of the subproject history that was imported into your project, and git subtree will attempt to build its history from there . If you used gitsubtree add ,you should never need this option .
--rejoin This option is only valid for the split command . After splitting, merge the newly created synthetic history back into your main project . That way, future splits can search only the part of history that has been added since the most recent --rejoin . If your split commits end up merged into the upstream subproject, and then you want to get the latest upstream version, this will allow git merge algorithm to more intelligently avoid conflicts (since it knows these synthetic commits are already part of the upstream repository) . Unfortunately, using this option results in gitlog showing an extra copy of every new commit that was created (the original, and the synthetic one) . If you do all your merges with --squash ,don use --rejoin when you split, because you don want the subproject history to be part of your project anyway .
$ git subtree add --prefix=git -subtree --squash \ git://github .com/apenwarr/git -subtree .git master .RE master needs to be a valid remote ref and can be a different branch name You can omit the --squash flag, but doing so will increase the number of commits that are included in your local repository . We now have a ~/git -extensions/git -subtree directory containing code from the master branch of git://github .com/apenwarr/git -subtree .git in our git -extensions repository .
$ git clone git://git .kernel .org/pub/scm/git/git .git test -git $ cd test -git .RE gitweb (commit 1130ef3) was merged into git as of commit 0a8f4f0, after which it was no longer maintained separately . But imagine it had been maintained separately, and we wanted to extract git changes to gitweb since that time, to share with the upstream . You could do this: .RS 4
$ git subtree split --prefix=gitweb --annotate= (Aq(split) (Aq \ 0a8f4f0^ . . --onto=1130ef3 --rejoin \ --branch gitweb -latest $ gitk gitweb -latest $ git push git@github .com:whatever/gitweb .git gitweb -latest:master .RE (We use 0a8f4f0^. . because that means "all the changes from 0a8f4f0 to the current version, including 0a8f4f0 itself .") If gitweb had originally been merged using gitsubtree add (or a previous split had already been done with --rejoin specified) then you can do all your splits without having to remember any weird commit ids: .RS 4
$ git subtree split --prefix=gitweb --annotate= (Aq(split) (Aq --rejoin \ --branch gitweb -latest2 .RE And you can merge changes back in from the upstream project just as easily: .RS 4
$ git subtree pull --prefix=gitweb \ git@github .com:whatever/gitweb .git master .RE Or, using --squash ,you can actually rewind to an earlier version of gitweb: .RS 4
$ git subtree merge --prefix=gitweb --squash gitweb -latest~10 .RE Then make some changes: .RS 4
$ date >gitweb/myfile $ git add gitweb/myfile $ git commit -m (Aqcreated myfile (Aq .RE And fast forward again: .RS 4
$ git subtree merge --prefix=gitweb --squash gitweb -latest .RE And notice that your change is still intact: .RS 4
$ ls -l gitweb/myfile .RE And you can split it out and look at your changes versus the standard gitweb: .RS 4
git log gitweb -latest . .$(git subtree split --prefix=gitweb) .RE
$ <go to the new location> $ git init --bare .RE Back in your original directory: .RS 4
$ git subtree split --prefix=lib --annotate="(split)" -b split .RE Then push the new branch onto the new empty repository: .RS 4
$ git push <new -repo> split:master .RE
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