graphlog: bring back color to node symbol template

Follows up 3356bf61fa25. A ui object is required to render labels.

mercurial/cmdutil.py

@@ -2206,6 +2206,7 b' def _graphnodeformatter(ui, displayer):'
     def formatnode(repo, ctx):
         props['ctx'] = ctx
         props['repo'] = repo
+        props['ui'] = repo.ui
         props['revcache'] = {}
         return templater.stringify(templ('graphnode', **props))
     return formatnode

tests/test-glog.t

@@ -2407,4 +2407,11 b' node template with changeset_templater ('
   o |  5 null+5
   | |
 
+label() should just work in node template:
+
+  $ hg log -Gqr 7 --config extensions.color= --color=debug \
+  > --config ui.graphnodetemplate='{label("branch.{branch}", rev)}'
+  [branch.default|7]  [log.node|7:02dbb8e276b8]
+  |
+
   $ cd ..