Fix bug with empty inc and exc

This fixes an exception that showed up when importing patches

mercurial/util.py

@@ -144,8 +144,12 b' def matcher(repo, cwd, names, inc, exc, '
         
     patmatch = matchfn(pats, '$') or always
     filematch = matchfn(files, '(?:/|$)') or always
-    incmatch = matchfn(map(patkind, inc), '(?:/|$)') or always
-    excmatch = matchfn(map(patkind, exc), '(?:/|$)') or (lambda fn: False)
+    incmatch = always
+    if inc:
+        incmatch = matchfn(map(patkind, inc), '(?:/|$)')
+    excmatch = lambda fn: False
+    if exc:
+        excmatch = matchfn(map(patkind, exc), '(?:/|$)')
 
     return roots, lambda fn: (incmatch(fn) and not excmatch(fn) and
                               (fn.endswith('/') or