log: use correct phase info for parent field (issue4347)

Previously, there was a copy / paste error with using the current changeset's
phase information. We now look up the parent context explicitly.

The line was too long so it is stored into a variable first.

mercurial/cmdutil.py

@@ -879,9 +879,10 b' class changeset_printer(object):'
             self.ui.write(_("phase:       %s\n") % _(ctx.phasestr()),
                           label='log.phase')
         for parent in parents:
+            label = 'log.parent changeset.%s' % self.repo[parent[0]].phasestr()
             # i18n: column positioning for "hg log"
             self.ui.write(_("parent:      %d:%s\n") % parent,
-                          label='log.parent changeset.%s' % ctx.phasestr())
+                          label=label)
 
         if self.ui.debugflag:
             mnode = ctx.manifestnode()