hg: don't complain about missing repo with no args

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

hg: don't complain about missing repo with no args

manifest hash: d8172c0b583d6f2ff60cf49e74c1247de8d9d673
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.0 (GNU/Linux)

iD8DBQFCnVmeywK+sNU5EO8RAj79AJ4wN1SwC8+e1amxv+EAd6VKhpXXYgCeIPDK
iVX9Z0Ix8DiC3p8fquyhFwM=
=c6EH
-----END PGP SIGNATURE-----

hg

@@ -107,7 +107,7 b' try:'
     cmd = args[0]
     args = args[1:]
 except:
-    cmd = ""
+    cmd = "help"
 
 ui = hg.ui(options["verbose"], options["debug"], options["quiet"],
            not options["noninteractive"])