According to HG manual:
By default this command prints
revision number and changeset id,
tags, non-trivial parents, user, date
and time, and a summary for each
commit. When the -v/–verbose switch
is used, the list of changed files and
full commit message are shown.
I have tried hg log -v but still it does not show the trivial parents.
You can use the
--debugoption.