Sometimes, you know the revision you want to land but don't remember which branch it's on. Although arc branch allows you to discover this information, we could make it simpler by allowing arc land X to behave something like:

• Check if there's a branch/bookmark/etc named X.
• If not, and X looks like D123, check if there's an accepted revision with that monogram.
• If there is, and we can figure out which branch it's on, emit a message, pretend the user typed arc land <that branch>, and proceed normally.