Detach (move) subdirectory into separate Git repository
I have a Git repository which contains a number of subdirectories. Now I have found that one of the subdirectories is unrelated to the other and should be detached to a separate repository.
How can I do this while keeping the history of the files within the subdirectory?
I guess I could make a clone and remove the unwanted parts of each clone, but I suppose this would give me the complete tree when checking out an older revision etc. This might be acceptable, but I would prefer to be able to pretend that the two repositories doesn't have a shared history.
Just to make it clear, I have the following structure:
XYZ/
.git/
XY1/
ABC/
XY2/
But I would like this instead:
XYZ/
.git/
XY1/
XY2/
ABC/
.git/
ABC/
Update : This process is so common, that the git team made it much simpler with a new tool, git subtree . See here: Detach (move) subdirectory into separate Git repository
You want to clone your repository and then use git filter-branch to mark everything but the subdirectory you want in your new repo to be garbage-collected.
To clone your local repository:
git clone /XYZ /ABC
(Note: the repository will be cloned using hard-links, but that is not a problem since the hard-linked files will not be modified in themselves - new ones will be created.)
Now, let us preserve the interesting branches which we want to rewrite as well, and then remove the origin to avoid pushing there and to make sure that old commits will not be referenced by the origin:
cd /ABC
for i in branch1 br2 br3; do git branch -t $i origin/$i; done
git remote rm origin
or for all remote branches:
cd /ABC
for i in $(git branch -r | sed "s/.*origin///"); do git branch -t $i origin/$i; done
git remote rm origin
Now you might want to also remove tags which have no relation with the subproject; you can also do that later, but you might need to prune your repo again. I did not do so and got a WARNING: Ref 'refs/tags/v0.1' is unchanged for all tags (since they were all unrelated to the subproject); additionally, after removing such tags more space will be reclaimed. Apparently git filter-branch should be able to rewrite other tags, but I could not verify this. If you want to remove all tags, use git tag -l | xargs git tag -d git tag -l | xargs git tag -d .
Then use filter-branch and reset to exclude the other files, so they can be pruned. Let's also add --tag-name-filter cat --prune-empty to remove empty commits and to rewrite tags (note that this will have to strip their signature):
git filter-branch --tag-name-filter cat --prune-empty --subdirectory-filter ABC -- --all
or alternatively, to only rewrite the HEAD branch and ignore tags and other branches:
git filter-branch --tag-name-filter cat --prune-empty --subdirectory-filter ABC HEAD
Then delete the backup reflogs so the space can be truly reclaimed (although now the operation is destructive)
git reset --hard
git for-each-ref --format="%(refname)" refs/original/ | xargs -n 1 git update-ref -d
git reflog expire --expire=now --all
git gc --aggressive --prune=now
and now you have a local git repository of the ABC sub-directory with all its history preserved.
Note: For most uses, git filter-branch should indeed have the added parameter -- --all . Yes that's really dash dash space dash dash all . This needs to be the last parameters for the command. As Matli discovered, this keeps the project branches and tags included in the new repo.
Edit: various suggestions from comments below were incorporated to make sure, for instance, that the repository is actually shrunk (which was not always the case before).
The Easy Way™
It turns out that this is such a common and useful practice that the overlords of git made it really easy, but you have to have a newer version of git (>= 1.7.11 May 2012). See the appendix for how to install the latest git. Also, there's a real-world example in the walkthrough below.
Prepare the old repo
pushd <big-repo>
git subtree split -P <name-of-folder> -b <name-of-new-branch>
popd
Note: <name-of-folder> must NOT contain leading or trailing characters. For instance, the folder named subproject MUST be passed as subproject , NOT ./subproject/
Note for windows users: when your folder depth is > 1, <name-of-folder> must have *nix style folder separator (/). For instance, the folder named path1path2subproject MUST be passed as path1/path2/subproject
Create the new repo
mkdir <new-repo>
pushd <new-repo>
git init
git pull </path/to/big-repo> <name-of-new-branch>
Link the new repo to Github or wherever
git remote add origin <git@github.com:my-user/new-repo.git>
git push origin -u master
Cleanup, if desired
popd # get out of <new-repo>
pushd <big-repo>
git rm -rf <name-of-folder>
Note : This leaves all the historical references in the repository.See the Appendix below if you're actually concerned about having committed a password or you need to decreasing the file size of your .git folder.
...
Walkthrough
These are the same steps as above , but following my exact steps for my repository instead of using <meta-named-things> .
Here's a project I have for implementing JavaScript browser modules in node:
tree ~/Code/node-browser-compat
node-browser-compat
├── ArrayBuffer
├── Audio
├── Blob
├── FormData
├── atob
├── btoa
├── location
└── navigator
I want to split out a single folder, btoa , into a separate git repository
pushd ~/Code/node-browser-compat/
git subtree split -P btoa -b btoa-only
popd
I now have a new branch, btoa-only , that only has commits for btoa and I want to create a new repository.
mkdir ~/Code/btoa/
pushd ~/Code/btoa/
git init
git pull ~/Code/node-browser-compat btoa-only
Next I create a new repo on Github or bitbucket, or whatever and add it is the origin (btw, "origin" is just a convention, not part of the command - you could call it "remote-server" or whatever you like)
git remote add origin git@github.com:node-browser-compat/btoa.git
git push origin -u master
Happy day!
Note: If you created a repo with a README.md , .gitignore and LICENSE , you will need to pull first:
git pull origin -u master
git push origin -u master
Lastly, I'll want to remove the folder from the bigger repo
git rm -rf btoa
...
Appendix
Latest git on OS X
To get the latest version of git:
brew install git
To get brew for OS X:
http://brew.sh
Latest git on Ubuntu
sudo apt-get update
sudo apt-get install git
git --version
If that doesn't work (you have a very old version of ubuntu), try
sudo add-apt-repository ppa:git-core/ppa
sudo apt-get update
sudo apt-get install git
If that still doesn't work, try
sudo chmod +x /usr/share/doc/git/contrib/subtree/git-subtree.sh
sudo ln -s
/usr/share/doc/git/contrib/subtree/git-subtree.sh
/usr/lib/git-core/git-subtree
Thanks to rui.araujo from the comments.
clearing your history
By default removing files from git doesn't actually remove them from git, it just commits that they aren't there anymore. If you want to actually remove the historical references (ie you have a committed a password), you need to do this:
git filter-branch --prune-empty --tree-filter 'rm -rf <name-of-folder>' HEAD
After that you can check that your file or folder no longer shows up in the git history at all
git log -- <name-of-folder> # should show nothing
However, you can't "push" deletes to github and the like. If you try you'll get an error and you'll have to git pull before you can git push - and then you're back to having everything in your history.
So if you want to delete history from the "origin" - meaning to delete it from github, bitbucket, etc - you'll need to delete the repo and re-push a pruned copy of the repo. But wait - there's more ! - If you're really concerned about getting rid of a password or something like that you'll need to prune the backup (see below).
making .git smaller
The aforementioned delete history command still leaves behind a bunch of backup files - because git is all too kind in helping you to not ruin your repo by accident. It will eventually deleted orphaned files over the days and months, but it leaves them there for a while in case you realize that you accidentally deleted something you didn't want to.
So if you really want to empty the trash to reduce the clone size of a repo immediately you have to do all of this really weird stuff:
rm -rf .git/refs/original/ &&
git reflog expire --all &&
git gc --aggressive --prune=now
git reflog expire --all --expire-unreachable=0
git repack -A -d
git prune
That said, I'd recommend not performing these steps unless you know that you need to - just in case you did prune the wrong subdirectory, y'know? The backup files shouldn't get cloned when you push the repo, they'll just be in your local copy.
Credit
Paul's answer creates a new repository containing /ABC, but does not remove /ABC from within /XYZ. The following command will remove /ABC from within /XYZ:
git filter-branch --tree-filter "rm -rf ABC" --prune-empty HEAD
Of course, test it in a 'clone --no-hardlinks' repository first, and follow it with the reset, gc and prune commands Paul lists.
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