Add a Mercurial dates plugin.

Basically just about the same as the Git dates plugin, but using
hg instead of git.

hyde/ext/plugins/vcs.py

@@ -66,3 +66,52 @@ class GitDatesPlugin(Plugin):
                     modified = modified.replace(tzinfo=None)
                     resource.meta.modified = modified
 
+
+#
+# Mercurial Dates
+#
+
+class MercurialDatesPlugin(Plugin):
+    """
+    Extract creation and last modification date from mercurial and
+    include them in the meta data if they are set to "hg". Creation
+    date is put in `created` and last modification date in `modified`.
+    """
+
+    def __init__(self, site):
+        super(MercurialDatesPlugin, self).__init__(site)
+
+    def begin_site(self):
+        """
+        Initialize plugin. Retrieve dates from mercurial
+        """
+        for node in self.site.content.walk():
+            for resource in node.resources:
+                created = None
+                modified = None
+                try:
+                    created = resource.meta.created
+                    modified = resource.meta.modified
+                except AttributeError:
+                    pass
+                # Everything is already overrided
+                if created != "hg" and modified != "hg":
+                    continue
+                # Run hg log --template={date|isodatesec}
+                try:
+                    commits = subprocess.check_output(["hg", "log", "--template={date|isodatesec}\n",
+                                                       resource.path]).split('\n')
+                except subprocess.CalledProcessError:
+                    self.logger.warning("Unable to get mercurial history for [%s]" % resource)
+                    continue
+                commits = commits[:-1]
+                if not commits:
+                    self.logger.warning("No mercurial history for [%s]" % resource)
+                    continue
+                if created == "hg":
+                    created = parse(commits[-1].strip())
+                    resource.meta.created = created
+                if modified == "hg":
+                    modified = parse(commits[0].strip())
+                    resource.meta.modified = modified
+