Joining cg-*-id

Hello!

I believe Cogito should keep the command list short. When the *-id utilities got the cg-prefix, the list became longer by 3 commands.

What if we join cg-commit-id, cg-parent-id and cg-tree-id into one cg-id (or cg-admin-id) utility? It would work like cg-commit-id in absence of switches, -p would make it work like cg-parent-id, and -t would make it cg-tree-id.

Alternatively, this functionality should go to git. It's low-level enough to be there.