I needed to copy a directory between two git repositories while preserving its history. I found some good instructions at http://gbayer.com/development/moving-files-from-one-git-repository-to-another-preserving-history/, which got me started, but I figured out a way to avoid having to move all the files into their directory again (lines 5-6 in Greg’s instructions) by reversing the filter to remove everything I don’t want instead of only including the directory I want. Here are the steps (the idea is the same as in Greg’s post, so please read that to get the explanation, I’m only listing the commands here for reference):
Get files ready for the move
(directory1 is the one you want to preserve)
git clone git-repository-A-url repo-A-tmp-dir
cd repo-A-tmp
git remote rm origin # for safety
git filter-branch --tree-filter 'rm -rf $(git ls-files | egrep -v directory1)' -- --all
(2016-06-08: update thanks to Pawel Veselov, using git ls-files instead of ls in the last command)
The last line replaces lines 4-8 in the original instructions.
At this point you should verify that only directory1 remains in the repository, with the correct history. I used the following command to verify that only commits related to my desired directory remained:
git log -p | grep '^diff ' | grep -v directory1
Merge files into the new repository
These steps are identical from Greg’s instructions.
git clone git-repository-B-url
cd git-repository-B-dir
git remote add repo-A-branch repo-A-tmp-dir
git pull repo-A-branch master
git remote rm repo-A-branch