Make it work like `git commit`

[awentzonline]

That would be cooler.

[awentzonline]

Maybe it should amend an existing commit, instead.

[pirate]

Since coolmit no longer needs to take the commit message as an argument, it would be nice to have an interface which just amends HEAD commit to have the desired prefix with no other arguments.

coolmitify cafe                    # amends HEAD commit to have "cafe" prefix
coolmitify --commit 9eb741c cafe   # amends 9eb741c commit to have "cafe" prefix, and rebases any necessary commits after it

Not a priority though, it works pretty great as-is right now.

[awentzonline]

I've changed it up so HEAD is updated which feels a lot nicer. I'm going to leave this open as a reminder to add the --commit and rebase option. Will publish to pypi when I get home later today.