Am I imagining a `git commit --fixup` helper tool that, given a staged change in a hunk of a file present in a previous commit, will automatically find that commit and `--fixup` that commit?

I'm fed up of noticing a problem, then `git log --oneline` and then copypasta a SHA and then `git rebase -i`, and then I notice another thing that's bad and the process starts over.

#Git #SoftwareDevelopment #DeveloperTooling #DevEx

Yes! Thanks, @rgarner, https://github.com/tummychow/git-absorb is what I was thinking of!
GitHub - tummychow/git-absorb: git commit --fixup, but automatic

git commit --fixup, but automatic. Contribute to tummychow/git-absorb development by creating an account on GitHub.

GitHub
@issyl0 git absorb is what you're describing I think
That would be a really handy tool, especially for streamlining the fixup process and reducing context switching. It sounds feasible with a clever script or git extension.