context: use manifest.find() instead of two separate calls

I noticed this while debugging an extension that's implementing the manifest
interface. Always nice to save a function call.

Differential Revision: https://phab.mercurial-scm.org/D8109

mercurial/context.py

@@ -267,7 +267,7 b' class basectx(object):'
     def _fileinfo(self, path):
         if '_manifest' in self.__dict__:
             try:
-                return self._manifest[path], self._manifest.flags(path)
+                return self._manifest.find(path)
             except KeyError:
                 raise error.ManifestLookupError(
                     self._node, path, _(b'not found in manifest')