match: let 'path:.' and 'path:' match everything (issue4687)

Previously, both queries exited with code 1, printing nothing.  The pattern in
the latter query is normalized to '.', so it is really the same case.

mercurial/match.py

@@ -407,6 +407,8 b' def _regex(kind, pat, globsuffix):'
     if kind == 're':
         return pat
     if kind == 'path':
+        if pat == '.':
+            return ''
         return '^' + util.re.escape(pat) + '(?:/|$)'
     if kind == 'relglob':
         return '(?:|.*/)' + _globre(pat) + globsuffix

tests/test-locate.t

@@ -106,6 +106,19 b' Issue294: hg remove --after dir fails wh'
   $ mkdir otherdir
   $ cd otherdir
 
+  $ hg files path:
+  ../b (glob)
+  ../dir.h/foo (glob)
+  ../t.h (glob)
+  ../t/e.h (glob)
+  ../t/x (glob)
+  $ hg files path:.
+  ../b (glob)
+  ../dir.h/foo (glob)
+  ../t.h (glob)
+  ../t/e.h (glob)
+  ../t/x (glob)
+
   $ hg locate b
   ../b (glob)
   ../t/b (glob)