How can I move a single directory from a git repository to a new repository whilst maintaining the history?

Question

I have inherited a git repository containing multiple projects in separate directories. I'd like to split the repository into new individual repositories, one for each project and then have the master repository contain the projects as submodules. I'd like to do all this whilst maintaining the revision history of the individual projects if possible.

I could clone the repository for each project and remove all the other projects each time, but it there a better way to avoid having the cloned history in each new project repository?

Answer 1

The point of git is that the history is embodied in each commit by hashing the parent commit. You could "replay" the commits (this is essentially how the svn-importer works) into a new repository and only keeping each sub-project. This, however, would destroy the meaning of the commit hashes. If you have no problem with that then so be it.

In the past I've just cloned it and moved on. This makes things larger but disk space is cheap; my time is expensive.

I also don't know of any tools to splice out a directory. I suppose you could git-log on the directory to find all commits on it then replay the commits with something like git-fast-export?

Answer 2

You can use git filter-branch to rewrite the history of a project. From the documentation:

To rewrite the repository to look as if foodir/ had been its project root, and discard all other history:

git filter-branch --subdirectory-filter foodir -- --all

Make several copies of your repo, do that for each subdirectory you want to split out, and you should wind up with what you're looking for.

Answer 3

Have you seen detach-subdirectory-into-separate-git-repository ? This helped me a lot.