I usually submit a list of commits for review. If I have:
git commit --amend
You can use git rebase, for example, if you want to modify back to commit
$ git rebase --interactive 'bbc643cd^'
In the default editor, modify
edit in the line whose commit you want to modify. Make your changes and then commit them with the same message you had before:
$ git commit --all --amend --no-edit
to modify the commit, and after that
$ git rebase --continue
to return back to the previous head commit.
WARNING: Note that this will change the SHA-1 of that commit as well as all children -- in other words, this rewrites the history from that point forward. You can break repos doing this if you push using the command
git push --force