narrow: remove narrowrevlog

Core now automatically enables ellipsis support on revlogs when
repositories have narrow enabled. So, we no longer need to globally
register the revlog flag as part of activating the narrow extension
and this code can be deleted.

A side effect of this change is that repositories will now raise an
error on encountering an ellipsis flag when the narrow extension is
loaded. Previously, loading the narrow extension on a non-narrow repo
could result in silent usage of the ellipsis flag. This could lead
to undetected bugs. I think the new behavior is more correct.

Differential Revision: https://phab.mercurial-scm.org/D4649

hgext/narrow/TODO.rst

@@ -7,18 +7,11 b' about the filtering of status being done'
 came up the import to hgext, but nobody's got concrete improvement
 ideas as of then.
 
-Fold most (or preferably all) of narrowrevlog.py into core.
-
-Address commentary in narrowrevlog.excludedmanifestrevlog.add -
+Address commentary in manifest.excludedmanifestrevlog.add -
 specifically we should improve the collaboration with core so that
 add() never gets called on an excluded directory and we can improve
 the stand-in to raise a ProgrammingError.
 
-Figure out how to correctly produce narrowmanifestrevlog and
-narrowfilelog instances instead of monkeypatching regular revlogs at
-runtime to our subclass. Even better, merge the narrowing logic
-directly into core.
-
 Reason more completely about rename-filtering logic in
 narrowfilelog. There could be some surprises lurking there.
 

hgext/narrow/__init__.py

@@ -28,7 +28,6 b' from . import ('
     narrowcopies,
     narrowpatch,
     narrowrepo,
-    narrowrevlog,
     narrowtemplates,
     narrowwirepeer,
 )
@@ -58,7 +57,6 b' def featuresetup(ui, features):'
 def uisetup(ui):
     """Wraps user-facing mercurial commands with narrow-aware versions."""
     localrepo.featuresetupfuncs.add(featuresetup)
-    narrowrevlog.setup()
     narrowbundle2.setup()
     narrowcommands.setup()
     narrowwirepeer.uisetup()