In Git, how do you apply a commit of bug fix to the other newer branches?

Question

If I have a public Git repository that contains 3 branches like the following:

  (release-to-customerA)
      |
      U               (master)
     /                    |
A---B---C---D---E ... S---T 
        |
    (release-to-customerB)

where commit 'B' was the original release version and commit 'U' resolved some bugs in 'B'. I want to apply the commit 'U' to both master and release-to-customerB branch, and when the next time I deliver a new release to the customers based on the commit 'D', 'E', ... 'T', I want the commit 'U' included. What is the cleanest way to do it?

I know that git rebase or git cherry-pick may do the trick in my local repository, but will I screw up the history when I submit the rebased work to the public repository?

Thanks for the answers.

Answer 1

You don't need to rebase for this particular operation, cherry-picking is fine:

git checkout checkout release-to-customerB
git cherry-pick U
git checkout master
git cherry-pick U

Cherry-picking only creates new commits and does not rewrite history, so it's always safe even if you later push to another repository.

Answer 2

Though cherry-picking will work, I'm not sure why you'd want to. It creates duplicate commits, which can cause problems if you ever want to merge. Indeed, this appears to be a case where you want to merge!

  (bugfixB, releaseA)
        --------------------- Y (master)
       /                     /
      U---X (releaseB)      /
     /   /                 /
A---B---C---D---E ... S---T

Note that I added a branch name bugfixB - this is a very general idea. The commit U should be made on a branch whose purpose is to fix B (it could be several commits). That branch should then be merged into all branches which need the bugfix - in this case, releaseA, releaseB, and master.

 git checkout -b bugfixB <SHA1 of B>
 # fix things, add changes
 git commit

 # for each branch...
 git checkout releaseA
 git merge bugfixB
 git checkout releaseB
 git merge bugfixB
 git checkout master
 git merge bugfixB

Answer 3

You shouldn't rebase in this situation, since clearly other people have seen commits C through T.

As Greg said, you can use git-cherry-pick to get just U; but, this will create a new commit with the same diff but a different ID. If you want to get all commits in release-to-customerA into release-to-customerB and master, you can use git-merge like so:

git checkout release-to-customerB
git merge release-to-customerA

git checkout master
git merge release-to-customerA