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

I wrote a little shell function called gcf to perform the fixup commit and the rebase automatically:

$ git add -p

  ... select hunks for the patch with y/n ...

$ gcf 

  That commits the fixup and does the rebase.  Done!  You can get back to coding.

For example, you can patch the second commit before the latest with: gcf HEAD~~

Here is the function. You can paste it into your ~/.bashrc

git_commit_immediate_fixup() {
  local commit_to_amend="$1"
  if [ -z "$commit_to_amend" ]; then
    echo "You must provide a commit to fixup!"; return 1
  fi

  # Get a static commit ref in case the commit is something relative like HEAD~
  commit_to_amend="$(git rev-parse "${commit_to_amend}")" || return 2

  #echo ">> Committing"
  git commit --no-verify --fixup "${commit_to_amend}" || return 3

  #echo ">> Performing rebase"
  EDITOR=true git rebase --interactive --autosquash --autostash \
                --rebase-merges --no-fork-point "${commit_to_amend}~"
}

alias gcf='git_commit_immediate_fixup'

It uses --autostash to stash and pop any uncommitted changes if necessary.

--autosquash requires an --interactive rebase, but we avoid the interaction by using a dummy EDITOR.

--no-fork-point protects commits from being silently dropped in rare situations (when you have forked off a new branch, and someone has already rebased past commits).