unfinishedstate: suggested `hg update .` (including `.`) to complete update

`hg update` can update to a different and undesired commit. For users
who have commands.update.requiredest=yes, it's even an error to run
just `hg update.

Differential Revision: https://phab.mercurial-scm.org/D6956

mercurial/state.py

@@ -201,7 +201,7 b' addunfinished('
     'update', fname='updatestate', clearable=True,
     cmdmsg=_('last update was interrupted'),
     cmdhint=_("use 'hg update' to get a consistent checkout"),
-    statushint=_("To continue:    hg update")
+    statushint=_("To continue:    hg update .")
 )
 addunfinished(
     'bisect', fname='bisect.state', allowcommit=True, reportonly=True,

tests/test-merge1.t

@@ -49,7 +49,7 b' Detect interrupted update by hg status -'
   ? b/nonempty
   # The repository is in an unfinished *update* state.
   
-  # To continue:    hg update
+  # To continue:    hg update .
   
 
   $ rm b/nonempty