How to extract a git subdirectory and make a submodule out of it?
I started a project some months ago and stored everything within a main directory. In my main directory "Project" there are several subdirectories containing different things: Project/paper contains a document written in LaTeX Project/sourcecode/RailsApp contains my rails app.
"Project" is GITified and there have been a lot of commits in both "paper" and "RailsApp" directory. Now, as I'd like to use cruisecontrol.rb for my "RailsApp" I wonder if there is a way to make a submodule out of "RailsApp" without losing the history.
Answer
Nowadays there's a much easier way to do it than manually using git filter-branch: git subtree
Installation
NOTE git-subtree is now part of git (if you install contrib) as of 1.7.11, so you might already have it installed. You may check by executing git subtree.
To install git-subtree from source (for older versions of git):
git clone https://github.com/apenwarr/git-subtree.git
cd git-subtree
sudo rsync -a ./git-subtree.sh /usr/local/bin/git-subtree
Or if you want the man pages and all
make doc
make install
Usage
Split a larger into smaller chunks:
# Go into the project root
cd ~/my-project
# Create a branch which only contains commits for the children of 'foo'
git subtree split --prefix=foo --branch=foo-only
# Remove 'foo' from the project
git rm -rf ./foo
# Create a git repo for 'foo' (assuming we already created it on github)
mkdir foo
pushd foo
git init
git remote add origin [email protected]:my-user/new-project.git
git pull ../ foo-only
git push origin -u master
popd
# Add 'foo' as a git submodule to `my-project`
git submodule add [email protected]:my-user/new-project.git foo
For detailed documentation (man page), please read git-subtree.txt.