How can I easily fixup a past commit?

Question

I just read amending a single file in a past commit in git but unfortunately the accepted solution \'reorders\' the commits, which is not what I want. So here\'s my question

Answer 1

commit --fixup and rebase --autosquash are great, but they don't do enough. When I have a sequence of commits A-B-C and I write some more changes in my working tree which belong in one or more of those existing commits, I have to manually look at the history, decide which changes belong in which commits, stage them and create the fixup! commits. But git already has access to enough information to be able to do all that for me, so I've written a Perl script which does just that.

For each hunk in git diff the script uses git blame to find the commit that last touched the relevant lines, and calls git commit --fixup to write the appropriate fixup! commits, essentially doing the same thing I was doing manually before.

If you find it useful, please feel free to improve and iterate on it and maybe one day we'll get such a feature in git proper. I'd love to see a tool that can understand how a merge conflict should be resolved when it has been introduced by an interactive rebase.