'<rev>{caret}0' means the commit itself and is used when '<rev>' is the
object name of a tag object that refers to a commit object.
-'<rev>{tilde}<n>', e.g. 'master{tilde}3'::
+'<rev>{tilde}[<n>]', e.g. 'HEAD{tilde}, master{tilde}3'::
+ A suffix '{tilde}' to a revision parameter means the first parent of
+ that commit object.
A suffix '{tilde}<n>' to a revision parameter means the commit
object that is the <n>th generation ancestor of the named
commit object, following only the first parents. I.e. '<rev>{tilde}3' is