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.