[BUG] git commit --allow-empty-message -m '' fails

From: Josh Hagins <hagins.josh@gmail.com>
Date: May 1, 2015, 23:31 UTC
Message-ID: <CANuW5x0eKVAToG76rJr6+n-Fdg7E5c8mHb8NvnQUT2PBzxjjPQ@mail.gmail.com>

When passed the `--allow-empty-message` flag with no `-m`, `git commit` will open the editor and allow you to exit with an empty message, as expected.

However, when passed `-m ''` in addition to `--allow-empty-message`, the commit fails. Example below:

    $ git commit -a --allow-empty-message -m ''
    error: switch `m' requires a value
    usage: git commit [<options>] [--] <pathspec>...
    ...

Shouldn't the `-m` switch know whether the `--allow-empty-message` flag has been passed?

Thanks, Josh