revset: fix a crash in parents() when 'wdir()' is in the set

revset: fix a crash in parents() when 'wdir()' is in the set

The crash was "TypeError: expected string or Unicode object, NoneType found"
down in revlog.parentrevs().  This fixes heads() too (which is where I found
it.)

--- a/mercurial/revset.py	Sun Jun 28 13:38:03 2015 -0400
+++ b/mercurial/revset.py	Mon Jun 29 10:34:56 2015 -0400
@@ -1468,7 +1468,10 @@
         ps = set()
         cl = repo.changelog
         for r in getset(repo, fullreposet(repo), x):
-            ps.update(cl.parentrevs(r))
+            if r is None:
+                ps.update(p.rev() for p in repo[r].parents())
+            else:
+                ps.update(cl.parentrevs(r))
     ps -= set([node.nullrev])
     return subset & ps
 

--- a/tests/test-add.t	Sun Jun 28 13:38:03 2015 -0400
+++ b/tests/test-add.t	Mon Jun 29 10:34:56 2015 -0400
@@ -75,6 +75,13 @@
 
   $ hg ci -m 0 --traceback
 
+  $ hg log -r "heads(. or wdir() & file('**'))"
+  changeset:   0:* (glob)
+  tag:         tip
+  user:        test
+  date:        Thu Jan 01 00:00:00 1970 +0000
+  summary:     0
+  
 should fail
 
   $ hg add a
@@ -99,6 +106,15 @@
   M a
   ? a.orig
 
+wdir doesn't cause a crash, and can be dynamically selected if dirty
+
+  $ hg log -r "heads(. or wdir() & file('**'))"
+  changeset:   2:*+ (glob)
+  parent:      2:* (glob)
+  parent:      1:* (glob)
+  user:        test
+  date:        * (glob)
+  
 should fail
 
   $ hg add a