Modifying a commit of a branch from the corresponding commit from another branch

Question

I had a git repo that looked something like this:

c1->c2->c3->c4 (mainline)
              \
               \ c6->c7->c8 (other branch)

I created a new branch called my branch from c4 on mainline, and added a commit c5 to my branch . Now my git repo looks something like this.

               c5 (my branch)
               /
c1->c2->c3->c4/ (mainline)
              \
               \ c6->c7->c8 (other branch)

The c4 of mainline was in code review and I had to modify the c4 of mainline after I got suggestions. However the changes do not appear in the c4 of my branch . Is there any way I can get all c4 changes from mainline to the c4 of my branch ?

Edit: Eventually I will have to merge my branch to mainline and push c5 for review as well.

Answer 1

When you modified your commit c4 on the mainline branch, you created a new commit hash.

A way to fix it would be to restart from c4 and apply the changes of my branch :

git checkout mainline
git checkout <hash-of-c4>      # go to updated c4
git checkout -b my-branch-new  # create branch
git cherry-pick <hash-of-c5>   # apply c5

my-branch-new should have both the changes of c4 and of c5

---

Answer 2

I take it you mean c5 of my branch .

You should just be able to run git rebase -i mainbranch while on my branch , then commit the result, to get all of the later commits of mainline . That will put c5 ahead of any changes that you made on mainbranch .

Secondly, you could just run git merge mainline from my branch , but that would make a new merge commit which isn't always desireable.

A third option would be to just cherry-pick any commits with the hash from mainbranch into my branch .

See: https://git-scm.com/docs/git-rebase