localrepo: add requirement when narrow files creation option present

The previous commit taught hg.clone() to define a creation option
when file include or exclude patterns are passed.

This commit teaches the new repo creation code to convert that creation
option into a repository requirement.

While not yet used by the narrow extension, the eventual side-effect
of this change is that newly-created repositories will have the narrow
requirement from their creation onset. Currently, the requirement is
added to the repo at exchange.pull() time via a wrapped function in
the narrow extension.

Differential Revision: https://phab.mercurial-scm.org/D4537

mercurial/localrepo.py

@@ -2440,6 +2440,9 b' def newreporequirements(ui, createopts=N'
     if ui.configbool('format', 'internal-phase'):
         requirements.add('internal-phase')
 
+    if createopts.get('narrowfiles'):
+        requirements.add(repository.NARROW_REQUIREMENT)
+
     return requirements
 
 def filterknowncreateopts(ui, createopts):
@@ -2456,7 +2459,9 b' def filterknowncreateopts(ui, createopts'
     Extensions can wrap this function to filter out creation options
     they know how to handle.
     """
-    return dict(createopts)
+    known = {'narrowfiles'}
+
+    return {k: v for k, v in createopts.items() if k not in known}
 
 def createrepository(ui, wdirvfs, createopts=None):
     """Create a new repository in a vfs.