Git thinks a failing command doesn't exist

Has this been noted before:

    $ git rebase --continue
    .: 986: Can't open /home/avar/g/git/.git/rebase-merge/author-script
    git: 'rebase' is not a git command. See 'git --help'.
    Did you mean this?
            rebase

Rebase failed, but the help mechanism seems to just test the exit
code, or something similar.

Perhaps help_unknown_cmd could just check if the command it's
suggesting == what it says doesn't exist, if so the command probably
failed, but maybe there's a better solution.