namespaces: generate template keyword when registering a namespace

For any namespace, we generate a template keyword. For example, given a
namespace 'babar', we automatically have the ability to use it in a template:

hg log -r . -T '{babars % "King: {babar}\n"}'

Furthermore, we only generate this keyword for a namespace if one doesn't
already exist. This is necessary for 'branches' and 'bookmarks' since both of
those have concepts of 'current' (something outside the namespace api) and also
allows extensions to override default behavior if desired.

mercurial/namespaces.py

@@ -1,103 +1,111 b''
 from i18n import _
 from mercurial import util
+import templatekw
 
 def tolist(val):
     """
     a convenience method to return an empty list instead of None
     """
     if val is None:
         return []
     else:
         return [val]
 
 class namespaces(object):
     """
     provides an interface to register a generic many-to-many mapping between
     some (namespaced) names and nodes. The goal here is to control the
     pollution of jamming things into tags or bookmarks (in extension-land) and
     to simplify internal bits of mercurial: log output, tab completion, etc.
 
     More precisely, we define a list of names (the namespace), a mapping of
     names to nodes, and a mapping from nodes to names. Each mapping
     returns a list of nodes.
 
     Furthermore, each name mapping will be passed a name to lookup which might
     not be in its domain. In this case, each method should return an empty list
     and not raise an error.
 
     We'll have a dictionary '_names' where each key is a namespace and
     its value is a dictionary of functions:
       'templatename': name to use for templating (usually the singular form
                       of the plural namespace name)
       'namemap': function that takes a name and returns a list of nodes
       'nodemap': function that takes a node and returns a list of names
     """
 
     _names_version = 0
 
     def __init__(self):
         self._names = util.sortdict()
 
         addns = self.addnamespace
 
         # we need current mercurial named objects (bookmarks, tags, and
         # branches) to be initialized somewhere, so that place is here
         addns("bookmarks", "bookmark",
               lambda repo, name: tolist(repo._bookmarks.get(name)),
               lambda repo, name: repo.nodebookmarks(name))
 
         addns("tags", "tag",
               lambda repo, name: tolist(repo._tagscache.tags.get(name)),
               lambda repo, name: repo.nodetags(name))
 
         addns("branches", "branch",
               lambda repo, name: tolist(repo.branchtip(name)),
               lambda repo, node: [repo[node].branch()])
 
     def addnamespace(self, namespace, templatename, namemap, nodemap,
                      order=None):
         """
         register a namespace
 
         namespace: the name to be registered (in plural form)
         templatename: the name to use for templating
         namemap: function that inputs a node, output name(s)
         nodemap: function that inputs a name, output node(s)
         order: optional argument to specify the order of namespaces
                (e.g. 'branches' should be listed before 'bookmarks')
         """
         val = {'templatename': templatename,
                'namemap': namemap,
                'nodemap': nodemap}
         if order is not None:
             self._names.insert(order, namespace, val)
         else:
             self._names[namespace] = val
 
+        # we only generate a template keyword if one does not already exist
+        if namespace not in templatekw.keywords:
+            def generatekw(**args):
+                return templatekw.shownames(namespace, **args)
+
+            templatekw.keywords[namespace] = generatekw
+
     def singlenode(self, repo, name):
         """
         Return the 'best' node for the given name. Best means the first node
         in the first nonempty list returned by a name-to-nodes mapping function
         in the defined precedence order.
 
         Raises a KeyError if there is no such node.
         """
         for ns, v in self._names.iteritems():
             n = v['namemap'](repo, name)
             if n:
                 # return max revision number
                 if len(n) > 1:
                     cl = repo.changelog
                     maxrev = max(cl.rev(node) for node in n)
                     return cl.node(maxrev)
                 return n[0]
         raise KeyError(_('no such name: %s') % name)
 
     def templatename(self, namespace):
         """method that returns the template name of a namespace"""
         return self._names[namespace]['templatename']
 
     def names(self, repo, namespace, node):
         """method that returns a (sorted) list of names in a namespace that
         match a given node"""
         return sorted(self._names[namespace]['nodemap'](repo, node))