$ hg update 2
2 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg parents
changeset:
user: Bryan O'Sullivan <bos@serpentine.com>
summary: Introduce a typo into hello.c.
$ hg update
2 files updated, 0 files merged, 0 files removed, 0 files unresolved