statichttprepo: use new functions for requirements validation

The new code in localrepo for requirements gathering and validation
is more robust than scmutil.readrequires(). Let's port statichttprepo
to it.

Since scmutil.readrequires() is no longer used, it has been removed.

It is possible extensions were monkeypatching this to supplement the
set of supported requirements. But the proper way to do that is to
register a featuresetupfuncs. I'm comfortable forcing the API break
because featuresetupfuncs is more robust and has been supported for
a while.

.. api::

   ``scmutil.readrequires()`` has been removed.

   Use ``localrepo.featuresetupfuncs`` to register new repository
   requirements.

   Use ``localrepo.ensurerequirementsrecognized()`` to validate them.

Differential Revision: https://phab.mercurial-scm.org/D4570

mercurial/scmutil.py

@@ -1145,25 +1145,6 b' def dirstatecopy(ui, repo, wctx, src, ds'
         elif not dryrun:
             wctx.copy(origsrc, dst)
 
-def readrequires(opener, supported):
-    '''Reads and parses .hg/requires and checks if all entries found
-    are in the list of supported features.'''
-    requirements = set(opener.read("requires").splitlines())
-    missings = []
-    for r in requirements:
-        if r not in supported:
-            if not r or not r[0:1].isalnum():
-                raise error.RequirementError(_(".hg/requires file is corrupt"))
-            missings.append(r)
-    missings.sort()
-    if missings:
-        raise error.RequirementError(
-            _("repository requires features unknown to this Mercurial: %s")
-            % " ".join(missings),
-            hint=_("see https://mercurial-scm.org/wiki/MissingRequirement"
-                   " for more information"))
-    return requirements
-
 def writerequires(opener, requirements):
     with opener('requires', 'w') as fp:
         for r in sorted(requirements):

mercurial/statichttprepo.py

@@ -19,7 +19,6 b' from . import ('
     manifest,
     namespaces,
     pathutil,
-    scmutil,
     store,
     url,
     util,
@@ -156,7 +155,7 b' class statichttprepository(localrepo.loc'
         self.filtername = None
 
         try:
-            requirements = scmutil.readrequires(self.vfs, self.supported)
+            requirements = set(self.vfs.read(b'requires').splitlines())
         except IOError as inst:
             if inst.errno != errno.ENOENT:
                 raise
@@ -174,6 +173,10 b' class statichttprepository(localrepo.loc'
                 msg = _("'%s' does not appear to be an hg repository") % path
                 raise error.RepoError(msg)
 
+        supportedrequirements = localrepo.gathersupportedrequirements(ui)
+        localrepo.ensurerequirementsrecognized(requirements,
+                                               supportedrequirements)
+
         # setup store
         self.store = store.store(requirements, self.path, vfsclass)
         self.spath = self.store.path