How to nuke a commit before last commit

Question

Suppose I have 2 branches master and dev.

The dev branch is ahead of master by 2 commits, and neither of those commits is merged or pushed to any remote.

The dev branch looks like this:

dev A - B - C - D - E

Whereas, A is oldest, and E newest commit.

Id like to get to this state:

dev A - B - C - E

Basically I want to nuke the commit before the last commit, as if it never happened. There should be no conflicts either (E does not depend on D's changes).

Could I use interactive rebase?

Answer 1

I would use the itneractive form of rebase. While on dev (you need to have clean working copy):

git rebase -i HEAD~~

In your favourite text editor, you get a list of last 2 commits. Just comment/delete the line for the unwanted commit.

If HEAD depends on changes introduced by HEAD~, you could get merge conflicts and after you resolve them, you will loose your previous history (still available through the reflog, of course). I usually prefer this method.

If you want to conserve your previous history (and the unneeded commit), you should do

git checkout HEAD~~         # go to last good commit
git checkout -b new_branch  # create a new branch and forget about the original
git cherry_pick dev         # copy the commit on top of `dev` to `new_branch`

You will still get a conflict, but you won't be modifying the history of dev.

_{On the other hand, if the unwanted commit was on master and you didn't want to break anybody's build, you would do git revert HEAD~}