bdiff: switch to policy importer

# no-check-commit

contrib/check-py3-compat.py

@@ -17,7 +17,6 b' import traceback'
 
 # Modules that have both Python and C implementations.
 _dualmodules = (
-    'bdiff.py',
     'diffhelpers.py',
     'mpatch.py',
     'parsers.py',

contrib/import-checker.py

@@ -26,7 +26,6 b' allowsymbolimports = ('
 
 # Modules that have both Python and C implementations.
 _dualmodules = (
-    'bdiff.py',
     'diffhelpers.py',
     'mpatch.py',
     'parsers.py',

contrib/wix/dist.wxs

@@ -13,7 +13,7 b''
         <Component Id="libOutput" Guid="$(var.lib.guid)" Win64='$(var.IsX64)'>
           <File Name="library.zip" KeyPath="yes" />
           <File Name="mercurial.cext.base85.pyd" />
-          <File Name="mercurial.bdiff.pyd" />
+          <File Name="mercurial.cext.bdiff.pyd" />
           <File Name="mercurial.diffhelpers.pyd" />
           <File Name="mercurial.mpatch.pyd" />
           <File Name="mercurial.cext.osutil.pyd" />

mercurial/__init__.py

@@ -23,7 +23,6 b' modulepolicy = policy.policy'
 # Modules that have both Python and C implementations. See also the
 # set of .py files under mercurial/pure/.
 _dualmodules = {
-    'mercurial.bdiff',
     'mercurial.diffhelpers',
     'mercurial.mpatch',
     'mercurial.parsers',

mercurial/debugcommands.py

@@ -1026,11 +1026,11 b' def debuginstall(ui, **opts):'
         err = None
         try:
             from . import (
-                bdiff,
                 mpatch,
             )
             from .cext import (
                 base85,
+                bdiff,
                 osutil,
             )
             dir(bdiff), dir(mpatch), dir(base85), dir(osutil) # quiet pyflakes

mercurial/mdiff.py

@@ -13,13 +13,15 b' import zlib'
 
 from .i18n import _
 from . import (
-    bdiff,
     error,
     mpatch,
+    policy,
     pycompat,
     util,
 )
 
+bdiff = policy.importmod(r'bdiff')
+
 blocks = bdiff.blocks
 fixws = bdiff.fixws
 patches = mpatch.patches

mercurial/pure/bdiff.py

@@ -11,7 +11,7 b' import difflib'
 import re
 import struct
 
-from . import policy
+from .. import policy
 policynocffi = policy.policynocffi
 modulepolicy = policy.policy
 

setup.py

@@ -624,8 +624,8 b' extmodules = ['
     Extension('mercurial.cext.base85', ['mercurial/cext/base85.c'],
               include_dirs=common_include_dirs,
               depends=common_depends),
-    Extension('mercurial.bdiff', ['mercurial/bdiff.c',
-                                  'mercurial/bdiff_module.c'],
+    Extension('mercurial.cext.bdiff', ['mercurial/bdiff.c',
+                                       'mercurial/cext/bdiff.c'],
               include_dirs=common_include_dirs,
               depends=common_depends + ['mercurial/bdiff.h']),
     Extension('mercurial.diffhelpers', ['mercurial/diffhelpers.c'],