formatter: fill missing resources by formatter, not by resource mapper

While working on demand loading of ctx/fctx objects, I found it's weird
to support lookup in both directions. For instance, fctx can be loaded
from (ctx, path) pair, but ctx may also be derived from fctx.changectx()
in the original mapping. If the original mapping has had fctx but no ctx,
and if the new mapping provides {path}, we can't be sure if fctx should be
updated by fctx'.changectx()[path] or not.

This patch simply drops the support for the resolution in fctx -> ctx -> repo
direction.

mercurial/formatter.py

@@ -199,8 +199,13 b' class baseformatter(object):'
     def context(self, **ctxs):
         '''insert context objects to be used to render template keywords'''
         ctxs = pycompat.byteskwargs(ctxs)
-        assert all(k in {'ctx', 'fctx'} for k in ctxs)
+        assert all(k in {'repo', 'ctx', 'fctx'} for k in ctxs)
         if self._converter.storecontext:
+            # populate missing resources in fctx -> ctx -> repo order
+            if 'fctx' in ctxs and 'ctx' not in ctxs:
+                ctxs['ctx'] = ctxs['fctx'].changectx()
+            if 'ctx' in ctxs and 'repo' not in ctxs:
+                ctxs['repo'] = ctxs['ctx'].repo()
             self._item.update(ctxs)
     def datahint(self):
         '''set of field names to be referenced'''
@@ -578,27 +583,13 b' class templateresources(templater.resour'
         return self._resmap.get(key)
 
     def _hasctx(self, mapping):
-        return 'ctx' in mapping or 'fctx' in mapping
-
-    def _getctx(self, mapping, key):
-        ctx = mapping.get('ctx')
-        if ctx is not None:
-            return ctx
-        fctx = mapping.get('fctx')
-        if fctx is not None:
-            return fctx.changectx()
-
-    def _getrepo(self, mapping, key):
-        ctx = self._getctx(mapping, 'ctx')
-        if ctx is not None:
-            return ctx.repo()
-        return self._getsome(mapping, key)
+        return 'ctx' in mapping
 
     _gettermap = {
         'cache': _getsome,
-        'ctx': _getctx,
+        'ctx': _getsome,
         'fctx': _getsome,
-        'repo': _getrepo,
+        'repo': _getsome,
         'revcache': _getsome,
         'ui': _getsome,
     }