diff -r c4c8d0d1267f -r 0ea8b9576d7c mercurial/pure/diffhelpers.py
--- a/mercurial/pure/diffhelpers.py	Mon Apr 09 20:52:54 2018 +0900
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,71 +0,0 @@
-# diffhelpers.py - pure Python implementation of diffhelpers.c
-#
-# Copyright 2009 Matt Mackall <mpm@selenic.com> and others
-#
-# This software may be used and distributed according to the terms of the
-# GNU General Public License version 2 or any later version.
-
-from __future__ import absolute_import
-
-def addlines(fp, hunk, lena, lenb, a, b):
-    """Read lines from fp into the hunk
-
-    The hunk is parsed into two arrays, a and b. a gets the old state of
-    the text, b gets the new state. The control char from the hunk is saved
-    when inserting into a, but not b (for performance while deleting files.)
-    """
-    while True:
-        todoa = lena - len(a)
-        todob = lenb - len(b)
-        num = max(todoa, todob)
-        if num == 0:
-            break
-        for i in xrange(num):
-            s = fp.readline()
-            if s == "\\ No newline at end of file\n":
-                fixnewline(hunk, a, b)
-                continue
-            if s == "\n":
-                # Some patches may be missing the control char
-                # on empty lines. Supply a leading space.
-                s = " \n"
-            hunk.append(s)
-            if s.startswith('+'):
-                b.append(s[1:])
-            elif s.startswith('-'):
-                a.append(s)
-            else:
-                b.append(s[1:])
-                a.append(s)
-    return 0
-
-def fixnewline(hunk, a, b):
-    """Fix up the last lines of a and b when the patch has no newline at EOF"""
-    l = hunk[-1]
-    # tolerate CRLF in last line
-    if l.endswith('\r\n'):
-        hline = l[:-2]
-    else:
-        hline = l[:-1]
-
-    if hline.startswith((' ', '+')):
-        b[-1] = hline[1:]
-    if hline.startswith((' ', '-')):
-        a[-1] = hline
-    hunk[-1] = hline
-    return 0
-
-def testhunk(a, b, bstart):
-    """Compare the lines in a with the lines in b
-
-    a is assumed to have a control char at the start of each line, this char
-    is ignored in the compare.
-    """
-    alen = len(a)
-    blen = len(b)
-    if alen > blen - bstart:
-        return -1
-    for i in xrange(alen):
-        if a[i][1:] != b[i + bstart]:
-            return -1
-    return 0