command line templates: add formatnode filter
This will print a full hash node with --debug and a short one otherwise.
Use it with some default templates and in map-cmdline.default to print
the parents. This should fix issue538.
#header#
<title>Mercurial repositories index</title>
</head>
<body>
<h2>Mercurial Repositories</h2>
The specified repository "#repo|escape#" is unknown, sorry.
Please go back to the main repository list page.
#footer#