context: move handling of filtering error to revsymbol() (API) When changectx's constructor runs into various Filtered*Error, it creates an exception with a hint about using --hidden. This only makes sense when the revision was provided by the user (if we get e.g. a FilteredLookupError from repo[p1], then it's instead a programming error). Thus, I'm moving the handling into revsymbol(). Also changed "unfilteredrepo[changeid]" to "revsymbol(unfilteredrepo, changeid)" as part of the move. Differential Revision: https://phab.mercurial-scm.org/D3143

--- a/mercurial/localrepo.py	Thu Apr 05 17:56:24 2018 +0530
+++ b/mercurial/localrepo.py	Thu Apr 05 00:04:09 2018 -0700
@@ -802,7 +802,8 @@
         try:
             self[changeid]
             return True
-        except error.RepoLookupError:
+        except (error.RepoLookupError, error.FilteredIndexError,
+                error.FilteredLookupError):
             return False
 
     def __nonzero__(self):