obsutil: make obsfateprinter() less dependent on templater

joinfmt() is defined as 'lambda x: scmutil.formatchangeid(repo[x])' in
showsuccsandmarkers().

Function arguments are reordered so they look more normal.

mercurial/obsutil.py

@@ -832,7 +832,7 b' def markersoperations(markers):'
 
     return sorted(operations)
 
-def obsfateprinter(successors, markers, ui):
+def obsfateprinter(ui, repo, successors, markers, formatctx):
     """ Build a obsfate string for a single successorset using all obsfate
     related function defined in obsutil
     """
@@ -852,7 +852,7 b' def obsfateprinter(successors, markers, '
 
     # Successors
     if successors:
-        fmtsuccessors = [successors.joinfmt(succ) for succ in successors]
+        fmtsuccessors = [formatctx(repo[succ]) for succ in successors]
         line.append(" as %s" % ", ".join(fmtsuccessors))
 
     # Users

mercurial/templatekw.py

@@ -498,10 +498,13 b' def showobsfate(context, mapping):'
     succsandmarkers = showsuccsandmarkers(context, mapping)
 
     ui = context.resource(mapping, 'ui')
+    repo = context.resource(mapping, 'repo')
     values = []
 
     for x in succsandmarkers:
-        values.append(obsutil.obsfateprinter(x['successors'], x['markers'], ui))
+        v = obsutil.obsfateprinter(ui, repo, x['successors'], x['markers'],
+                                   scmutil.formatchangeid)
+        values.append(v)
 
     return compatlist(context, mapping, "fate", values)