--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mercurial/diffhelper.py	Sat May 05 18:06:45 2018 -0700
@@ -0,0 +1,77 @@
+# diffhelper.py - helper routines for patch
+#
+# 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
+
+from .i18n import _
+
+from . import (
+    error,
+)
+
+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 not s:
+                raise error.ParseError(_('incomplete hunk'))
+            if s == "\\ No newline at end of file\n":
+                fixnewline(hunk, a, b)
+                continue
+            if s == '\n' or s == '\r\n':
+                # Some patches may be missing the control char
+                # on empty lines. Supply a leading space.
+                s = ' ' + s
+            hunk.append(s)
+            if s.startswith('+'):
+                b.append(s[1:])
+            elif s.startswith('-'):
+                a.append(s)
+            else:
+                b.append(s[1:])
+                a.append(s)
+
+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
+
+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 or bstart < 0:
+        return False
+    for i in xrange(alen):
+        if a[i][1:] != b[i + bstart]:
+            return False
+    return True