util._matcher: use "." as the root of empty {rel,}path patterns

Should fix issue332. Really.

mercurial/util.py

@@ -492,7 +492,7 b' def _matcher(canonroot, cwd, names, inc,'
                 roots.append(root)
             elif kind in ('relpath', 'path'):
                 files.append((kind, name))
-                roots.append(name)
+                roots.append(name or '.')
             elif kind == 'relglob':
                 roots.append('.')
         return roots, pats + files, anypats

tests/test-revert

@@ -89,4 +89,6 b' echo %% issue332'
 hg ci -A -m b -d '1000001 0'
 echo foobar > b/b
 hg revert b
+echo foobar > b/b
+hg revert .
 true

tests/test-revert.out

@@ -61,3 +61,4 b' reverting a'
 %% issue332
 adding b/b
 reverting b/b
+reverting b/b