templater: set the correct phase for parents
Akin to f6371cc62d2a which did this for `hg log`, the following sets
the correct phase for the {phase} keyword when the context is a parent
of the current cset. This allows templates such as the following to be
defined,
parent = '{label("log.parent changeset.{phase}",
"parent: {rev}:{node|formatnode}")}\n'
which when called on a parent (e.g. with the `parents` template
keyword), will produce the correct phase.
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ echo 'base' > base
$ hg ci -Ambase
adding base
$ hg qnew -mmqbase mqbase
$ hg qsave
$ hg qrestore 2
restoring status: hg patches saved state