largefiles: avoid dynamically subclassing context instances

E.g. copies.pathcopies() compares context objects for equality and
basectx.__eq__ compares the type. But since largefiles was dynamically
creating classes, they would all be unequal. That led pathcopies(),
after some changes I made, to not short-circuit to get copy info only
from the dirstate. This patch fixes that short-circuiting (and other
places where context are being compared for equality).

Differential Revision: https://phab.mercurial-scm.org/D7143

hgext/largefiles/reposetup.py

@@ -15,6 +15,7 b' from mercurial.i18n import _'
 
 from mercurial import (
     error,
+    extensions,
     localrepo,
     match as matchmod,
     scmutil,
@@ -47,13 +48,14 b' def reposetup(ui, repo):'
             ctx = super(lfilesrepo, self).__getitem__(changeid)
             if self.lfstatus:
 
-                class lfilesctx(ctx.__class__):
-                    def files(self):
-                        filenames = super(lfilesctx, self).files()
+                def files(orig):
+                    filenames = orig()
                         return [lfutil.splitstandin(f) or f for f in filenames]
 
-                    def manifest(self):
-                        man1 = super(lfilesctx, self).manifest()
+                extensions.wrapfunction(ctx, 'files', files)
+
+                def manifest(orig):
+                    man1 = orig()
 
                         class lfilesmanifest(man1.__class__):
                             def __contains__(self, filename):
@@ -65,8 +67,9 b' def reposetup(ui, repo):'
                         man1.__class__ = lfilesmanifest
                         return man1
 
-                    def filectx(self, path, fileid=None, filelog=None):
-                        orig = super(lfilesctx, self).filectx
+                extensions.wrapfunction(ctx, 'manifest', manifest)
+
+                def filectx(orig, path, fileid=None, filelog=None):
                         try:
                             if filelog is not None:
                                 result = orig(path, fileid, filelog)
@@ -76,16 +79,15 b' def reposetup(ui, repo):'
                             # Adding a null character will cause Mercurial to
                             # identify this as a binary file.
                             if filelog is not None:
-                                result = orig(
-                                    lfutil.standin(path), fileid, filelog
-                                )
+                            result = orig(lfutil.standin(path), fileid, filelog)
                             else:
                                 result = orig(lfutil.standin(path), fileid)
                             olddata = result.data
                             result.data = lambda: olddata() + b'\0'
                         return result
 
-                ctx.__class__ = lfilesctx
+                extensions.wrapfunction(ctx, 'filectx', filectx)
+
             return ctx
 
         # Figure out the status of big files and insert them into the