mdiff: remove experimental.xdiff config and related code

Summary:
we have enabled xdiff for 5+ years, let's remove the experimental.xdiff
config

Reviewed By: quark-zju

Differential Revision: D54324349

fbshipit-source-id: e058bd77c8c48c2e809a4ea4649d1a3ccb2d53e7

eden/scm/sapling/configitems.py

@@ -275,7 +275,6 @@ def getitemregister(configtable):
 coreconfigitem("experimental", "sparse-read.min-gap-size", default="256K")
 coreconfigitem("experimental", "treemanifest", default=False)
 coreconfigitem("experimental", "uncommitondirtywdir", default=True)
-coreconfigitem("experimental", "xdiff", default=True)
 coreconfigitem("experimental", "gitcopytrace", default=True)
 coreconfigitem("extensions", ".*", default=None, generic=True)
 coreconfigitem("format", "aggressivemergedeltas", default=False)

eden/scm/sapling/dispatch.py

@@ -1090,10 +1090,6 @@ def print_time():
             elif rpath:
                 ui.warn(_("warning: --repository ignored\n"))
 
-            from . import match as matchmod, mdiff
-
-            mdiff.init(ui)
-
             ui.log("command", "%s\n", msg)
             if repo:
                 repo.dirstate.loginfo(ui, "pre")

eden/scm/sapling/mdiff.py

@@ -17,7 +17,7 @@
 import struct
 import zlib
 from hashlib import sha1
-from typing import Iterator, List, Optional, Pattern, Sized, Tuple, TYPE_CHECKING, Union
+from typing import Iterator, List, Optional, Pattern, Sized, Tuple, Union
 
 import bindings
 
@@ -28,13 +28,9 @@
 bdiff = bindings.cext.bdiff
 mpatch = bindings.cext.mpatch
 
-if TYPE_CHECKING:
-    import sapling
-
-
 _missing_newline_marker = b"\\ No newline at end of file\n"
 
-blocks = bdiff.blocks
+blocks = bindings.xdiff.blocks
 fixws = bdiff.fixws
 patches = mpatch.patches
 patchedsize = mpatch.patchedsize
@@ -44,12 +40,6 @@
     rb"(\t+| +|[a-zA-Z0-9_\x80-\xff]+|[^ \ta-zA-Z0-9_\x80-\xff])"
 )
 
-# called by dispatch.py
-def init(ui: "sapling.ui.ui") -> None:
-    if ui.configbool("experimental", "xdiff"):
-        global blocks
-        blocks = bindings.xdiff.blocks
-
 
 def splitnewlines(text: bytes) -> "List[bytes]":
     """like str.splitlines, but only split on newlines."""