repoview: issue a special message when filtering hidden changesets

Hidden changesets are by far the most common error case and is the only one[1]
that can reach the user. We move to a friendlier message with a hint about how
to access the data anyway. We should probably point to a help topic instead but
we do not have such a topic yet.

Example of the new output

  abort: hidden revision '4'!
  (use --hidden to access hidden revisions)


[1] Actually, filtering from "served" can also reach the user during certain
exchange operations.

mercurial/context.py

@@ -469,6 +469,10 b' class changectx(basectx):'
                 pass
         except (error.FilteredIndexError, error.FilteredLookupError,
                 error.FilteredRepoLookupError):
+            if repo.filtername == 'visible':
+                msg = _("hidden revision '%s'") % changeid
+                hint = _('use --hidden to access hidden revisions')
+                raise error.FilteredRepoLookupError(msg, hint=hint)
             msg = _("filtered revision '%s' (not in '%s' subset)")
             msg %= (changeid, repo.filtername)
             raise error.FilteredRepoLookupError(msg)

tests/test-log.t

@@ -1393,7 +1393,8 b' enable obsolete to test hidden feature'
   1:a765632148dc55d38c35c4f247c618701886cb2f
   0:9f758d63dcde62d547ebfb08e1e7ee96535f2b05
   $ hg log -r a
-  abort: filtered revision 'a' (not in 'visible' subset)!
+  abort: hidden revision 'a'!
+  (use --hidden to access hidden revisions)
   [255]
 
 test that parent prevent a changeset to be hidden

tests/test-obsolete.t

@@ -182,7 +182,8 b' check that various commands work well wi'
   abort: unknown revision '6'!
   [255]
   $ hg log -r 4
-  abort: filtered revision '4' (not in 'visible' subset)!
+  abort: hidden revision '4'!
+  (use --hidden to access hidden revisions)
   [255]
 
 Check that public changeset are not accounted as obsolete: