GIT: how do i do a partial merge from one branch to another one?

Question

I have commits A-B-C-D on one branch and want to merge A-B-C to another one.

I know that you could do git cherry-pick one by one, and my question is whether I could group these commits together and hopefully do a squash.

Answer 1

Like Autocracy said, git rebase is probably what you want.

An example:

Let's say you have A-B-C-D and want to merge A-B-C to Y. Creates a clone of C and rebase the clone onto Y:

git checkout -b C_copy C
git rebase --onto Y A~1 C_copy  # <= --onto [target] [source] [what]

Check if everything went well and resolve conflicts on your way if necessary.

Now you've got C_copy on top of Y, like this: Y-[A_copy]-[B-copy]-C_copy

You could edit that with an interactive rebase e.g. to squash it (assuming you're still on C_copy):

git rebase -i HEAD~3

If something goes awry, you can just throw away C_copy as it does not affect C.

Now you can either fast-forward Y to C_copy or merge it using git merge --no-ff (specify --no-commit to edit your commit if you wish):

git checkout Y
git merge --no-ff [--no-commit] C_copy

Answer 2

Shouldn't git checkout branch-to-merge-on; git merge tag-or-sha1-of-commit-c work?

The following does as I expect:

git init
touch init; git add init; git commit -m 'init'
git checkout -b abcd
touch a; git add a; git commit -m 'a'
touch b; git add b; git commit -m 'b'
touch c; git add c; git commit -m 'c'; git tag commit-c
touch d; git add d; git commit -m 'd'
git checkout master
touch e; git add e; git commit -m 'e'
git merge commit-c

resulting in

init -- e -- merged   <- (master)
 \           /   
  a -- b -- c -- d    <- (abcd)

This merges everything (up until a common ancestor (init) in this case) before c, but it looks like this is what you want to do. If not, then git rebaseing a-b-c-d elsewhere might be appropriate.