git move portion of old repository to a new repository

Question

I've a repository which contains several directories at the root, e.g.

gitroot/a
gitroot/b
gitroot/c

And I would like to create a new git repository from only the contents of a, whilst retaining its history. Is this possible? I've seen the sparse checkouts, but I'm not sure how I could use this to create a brand new repository (with relevant history) from a subdirectory.

Answer 1

After cloning your existing repository, you can use filter-branch

git filter-branch --subdirectory-filter a -- --all

After that;

git clean -d -f  // Remove untracked files from the working tree
git gc --aggressive // Cleanup unnecessary files and optimize the local repository
git prune  // Prune all unreachable objects from the object database