update: also use 'destupdate' for pull and unbundle

Update can also be performed by 'hg pull --update' and 'hg unbundle'. We use the
destupdate function in these case too.

mercurial/commands.py

@@ -5185,8 +5185,12 b' def postincoming(ui, repo, modheads, opt'
     if modheads == 0:
         return
     if optupdate:
-        checkout, movemarkfrom = bookmarks.calculateupdate(ui, repo, checkout)
         try:
+            brev = checkout
+            movemarkfrom = None
+            if not checkout:
+                updata =  destutil.destupdate(repo)
+                checkout, movemarkfrom, brev = updata
             ret = hg.update(repo, checkout)
         except error.Abort as inst:
             ui.warn(_("not updating: %s\n") % str(inst))