Re-doing a reverted merge in Git

Answer 1

You have to "revert the revert". Depends on how did you revert that, it may not be as easy as it sounds. Look at the official document on this topic.

---o---o---o---M---x---x---W---x---Y
              /
      ---A---B-------------------C---D

to allow:

---o---o---o---M---x---x-------x-------*
              /                       /
      ---A---B-------------------C---D

But does it all work? Sure it does. You can revert a merge, and from a purely technical angle, git did it very naturally and had no real troubles.
It just considered it a change from "state before merge" to "state after merge", and that was it.
Nothing complicated, nothing odd, nothing really dangerous. Git will do it without even thinking about it.

So from a technical angle, there's nothing wrong with reverting a merge, but from a workflow angle it's something that you generally should try to avoid.

If at all possible, for example, if you find a problem that got merged into the main tree, rather than revert the merge, try really hard to:

• bisect the problem down into the branch you merged, and just fix it,
• or try to revert the individual commit that caused it.

Yes, it's more complex, and no, it's not always going to work (sometimes the answer is: "oops, I really shouldn't have merged it, because it wasn't ready yet, and I really need to undo all of the merge"). So then you really should revert the merge, but when you want to re-do the merge, you now need to do it by reverting the revert.

Answer 2

Instead of using git-revert you could have used this command in the devel branch to throw away (undo) the wrong merge commit (instead of just reverting it).

git checkout devel
git reset --hard COMMIT_BEFORE_WRONG_MERGE

This will also adjust the contents of the working directory accordingly. Be careful:

• Save your changes in the develop branch (since the wrong merge) because they too will be erased by the git-reset. All commits after the one you specify as the git reset argument will be gone!
• Also, don't do this if your changes were already pulled from other repositories because the reset will rewrite history.

I recommend to study the git-reset man-page carefully before trying this.

Now, after the reset you can re-apply your changes in devel and then do

git checkout devel
git merge 28s

This will be a real merge from 28s into devel like the initial one (which is now erased from git's history).