Add revlog.parentrevs function. This allows one to walk the revision graph using only revision numbers, which can be faster than using revision hashes, especially for RevlogNG, where the parents of a revision are stored as revision numbers.

(the addremove command is deprecated; use add and remove --after instead)
adding dir/bar
adding foo
dir/bar
foo
(the addremove command is deprecated; use add and remove --after instead)
adding dir/bar_2
adding foo_2
dir/bar_2
foo_2