How to revert the second to last commit but not the last commit?

Question

Say I have four commits A-->B-->C-->D but C was terribly misguided. How can I undo C without losing the changes from D? I understand the basic functionality of git-revert and undoing commits, but I can't figure out how (if it is even possible) to undo a specific commit (not the latest) without having to redo the changes that came after it.

Answer 1

Revert

The git revert command is designed to do exactly this.

git revert <hash for C> 

This will create a new commit which reverses the change in C.

Rewrite History

You can also rewrite history. This is not generally recommended, and should only be used if you have a good reason to actually remove a commit from history (say, if it contains a password or something).

git rebase -i <hash for B> 

In the editor, just delete the line with the hash for C. The usual caveats apply if you have already pushed.

Non-interactive

Technically, all of these options involve some kind of merge resolution which means they cannot truly be non-interactive. The only difference is the resulting history. With git revert you get a history that looks like this:

A -> B -> C -> D -> E                     ^                     +--- reverts C 

With git rebase, you end up with a history that looks like this:

A -> B -----------> E 

You can of course just do git rebase --onto B C, instead of git rebase -i, but this is still an interactive process because you have to manually resolve any merge conflicts that can't be automatically resolved by the merge strategy.