localrepo: enable ellipsis flag on revlogs when repo is narrow

If the narrow requirement is present, revlogs created for that
repository will have the ellipsis flag enabled.

This is the same behavior that the narrow extension exhibits. Except
the ellipsis flag won't be enabled on repos/revlogs that don't have
the narrow requirement.

Differential Revision: https://phab.mercurial-scm.org/D4648

mercurial/localrepo.py

@@ -727,6 +727,9 b' def resolverevlogstorevfsoptions(ui, req'
         if r.startswith(b'exp-compression-'):
             options[b'compengine'] = r[len(b'exp-compression-'):]
 
+    if repository.NARROW_REQUIREMENT in requirements:
+        options[b'enableellipsis'] = True
+
     return options
 
 def makemain(**kwargs):