revert: drop requirement to use -r to revert with two parents This reduces documentation confusion between the need to: a) hg revert -a -r . (drop all changes from a merge) b) hg up -C . (drop the second parent entirely) Currently revert is one of two commands (the other being tag) that still complains about uncommitted merges, dating from its former use of a generic defaultrev function that aborted.

revert: simplify usage note This points people looking for other commands to the right place with a minimum of verbiage.

revert: rewrite help summary New users have a tendency to mistake 'revert' as the command to use to check out old revisions. They also occasionally mistake revert for a generalized undo (compare rollback). This version intentionally aims to avoid mentioning 'earlier' and thus intentionally no longer alludes to the (secondary) -r behavior (which in fact is not actually limited to 'earlier'). Instead, we mention checkout state, to convey that we can restore things to the way they were when checked out.