templater: add simple interface for unnamed template (API)

This provides a simpler API for callers which don't need full templating
stack. Instead of storing the given template as the name specified by topic,
use '' as the default template to be rendered.

mercurial/cmdutil.py

@@ -2297,7 +2297,7 b' def _graphnodeformatter(ui, displayer):'
         return templatekw.showgraphnode  # fast path for "{graphnode}"
 
     spec = templater.unquotestring(spec)
-    templ = formatter.maketemplater(ui, 'graphnode', spec)
+    templ = formatter.maketemplater(ui, spec)
     cache = {}
     if isinstance(displayer, changeset_templater):
         cache = displayer.cache  # reuse cache of slow templates
@@ -2309,7 +2309,7 b' def _graphnodeformatter(ui, displayer):'
         props['repo'] = repo
         props['ui'] = repo.ui
         props['revcache'] = {}
-        return templater.stringify(templ('graphnode', **props))
+        return templ.render(props)
     return formatnode
 
 def displaygraph(ui, repo, dag, displayer, edgefn, getrenamed=None,

mercurial/debugcommands.py

@@ -2121,9 +2121,9 b' def debugtemplate(ui, repo, tmpl, **opts'
             ui.note(("* expanded:\n"), templater.prettyformat(newtree), '\n')
 
     if revs is None:
-        k = 'debugtemplate'
-        t = formatter.maketemplater(ui, k, tmpl)
-        ui.write(templater.stringify(t(k, ui=ui, **props)))
+        t = formatter.maketemplater(ui, tmpl)
+        props['ui'] = ui
+        ui.write(t.render(props))
     else:
         displayer = cmdutil.makelogtemplater(ui, repo, tmpl)
         for r in revs:

mercurial/filemerge.py

@@ -534,10 +534,10 b' def _formatconflictmarker(repo, ctx, tem'
     props['templ'] = template
     props['ctx'] = ctx
     props['repo'] = repo
-    templateresult = template('conflictmarker', **props)
+    templateresult = template.render(props)
 
     label = ('%s:' % label).ljust(pad + 1)
-    mark = '%s %s' % (label, templater.stringify(templateresult))
+    mark = '%s %s' % (label, templateresult)
 
     if mark:
         mark = mark.splitlines()[0] # split for safety
@@ -566,7 +566,7 b' def _formatlabels(repo, fcd, fco, fca, l'
     ui = repo.ui
     template = ui.config('ui', 'mergemarkertemplate', _defaultconflictmarker)
     template = templater.unquotestring(template)
-    tmpl = formatter.maketemplater(ui, 'conflictmarker', template)
+    tmpl = formatter.maketemplater(ui, template)
 
     pad = max(len(l) for l in labels)
 

mercurial/formatter.py

@@ -431,10 +431,13 b' def loadtemplater(ui, spec, cache=None):'
     assert not (spec.tmpl and spec.mapfile)
     if spec.mapfile:
         return templater.templater.frommapfile(spec.mapfile, cache=cache)
-    return maketemplater(ui, spec.ref, spec.tmpl, cache=cache)
+    return _maketemplater(ui, spec.ref, spec.tmpl, cache=cache)
 
-def maketemplater(ui, topic, tmpl, cache=None):
+def maketemplater(ui, tmpl, cache=None):
     """Create a templater from a string template 'tmpl'"""
+    return _maketemplater(ui, '', tmpl, cache=cache)
+
+def _maketemplater(ui, topic, tmpl, cache=None):
     aliases = ui.configitems('templatealias')
     t = templater.templater(cache=cache, aliases=aliases)
     if tmpl:

mercurial/templater.py

@@ -1298,6 +1298,10 b' class templater(object):'
                               (self.map[t][1], inst.args[1]))
         return self.cache[t]
 
+    def render(self, mapping):
+        """Render the default unnamed template and return result as string"""
+        return stringify(self('', **mapping))
+
     def __call__(self, t, **mapping):
         ttype = t in self.map and self.map[t][0] or 'default'
         if ttype not in self.ecache: