Show the full commit ID in a tooltip for the Commit field.
The Commit field shortens the commit ID if it's too long. It's still

useful to be able to see the full ID, though. Now, hovering over the

shortened ID will show a tooltip containing the full ID.

Posted a change with an abbreviated commit ID. Hovered over the abbreviated ID

and saw a tooltip with the full ID.
Posted a change against Mercurial that didn't abbreviate the commit ID. Hovered

over and never saw a tooltip.