How do I merge a sub directory in Git?

Question

Is it possible to merge only the changes for a sub-directory from a local Git branch to a remote Git branch or is it "all or nothing"?

For example, I have:<

Answer 1

Create a Git repository to contain both branch-a and branch-b:

git checkout branch-a
git diff branch-b dir-1 > a.diff
patch -R -p1 < a.diff