Why isn't the 'edit' command mentioned? It's one of the most useful features. It can be used for splitting commits, for example. Mark the commit you want to split to be edited. The commit replay is going to stop after that commit. Now:

  git reset HEAD^1 (NO --hard!)
  git commit --patch ...
  git rebase --continue

  git commit --patch --amend ...

  git stash
  git rebase --continue
  git stash pop