How to modify a specified commit?

Question

I usually submit a list of commits for review. If I have the following commits:

1. HEAD
2. Commit3
3. Commit2

Answer 1

git stash + rebase automation

For when I need to modify an old commit a lot of times for Gerrit reviews, I've been doing:

git-amend-old() (
  # Stash, apply to past commit, and rebase the current branch on to of the result.
  current_branch="$(git rev-parse --abbrev-ref HEAD)"
  apply_to="$1"
  git stash
  git checkout "$apply_to"
  git stash apply
  git add -u
  git commit --amend --no-edit
  new_sha="$(git log --format="%H" -n 1)"
  git checkout "$current_branch"
  git rebase --onto "$new_sha" "$apply_to"
)

GitHub upstream.

Usage:

• modify source file, no need to git add if already in repo
• git-amend-old $old_sha

I like this over --autosquash as it does not squash other unrelated fixups.