[feature request] allow directly committing untracked files

I often use 'git commit some-file -m 'some message'" to quickly make a commit, but this is annoying as it doesn't work if some-file is untracked, you first have to do 'git add some-file'. It would also be nice to do this with the `-a` option as well. Is there any reason why git does not let you do this? Would people be open to me making a patch that ads this? Would it need to be behind an option for backwards-compatibility?

— Isaac Oscar Gariano​