localrepo: recognize trivial request for '.'

Same logic as for `null`, this is a command request and skipping the revset
logic can avoid triggering the changelog filtering logic.

Differential Revision: https://phab.mercurial-scm.org/D7495

mercurial/localrepo.py

@@ -1708,6 +1708,10 b' class localrepository(object):'
         '''
         if specs == [b'null']:
             return revset.baseset([nullrev])
+        if specs == [b'.']:
+            quick_data = self._quick_access_changeid.get(b'.')
+            if quick_data is not None:
+                return revset.baseset([quick_data[0]])
         if user:
             m = revset.matchany(
                 self.ui,

tests/test-repo-filters-tiptoe.t

@@ -70,7 +70,6 b' Getting status of working copy'
 Getting data about the working copy parent
 
   $ hg log -r '.' -T "{node}\n{date}\n"
-  debug.filters: computing revision filter for "visible"
   c2932ca7786be30b67154d541a8764fae5532261
   0.00
 
@@ -111,8 +110,8 b' Getting working copy diff'
 exporting the current changeset
 
   $ hg export
+  exporting patch:
   debug.filters: computing revision filter for "visible"
-  exporting patch:
   # HG changeset patch
   # User test
   # Date 0 0