patch: better handling of sequence of offset patch hunks (issue1941)

The built-in patch implementation applied the hunks to the wrong lines of the
file if the file in the repo has been modified to skew the patch line numbers
and the file contains repetitive sequences of lines.

tests/test-patch-offset

@@ -0,0 +1,67 b''
+#!/bin/sh
+
+cat > writepatterns.py <<EOF
+import sys
+
+path = sys.argv[1]
+patterns = sys.argv[2:]
+
+fp = file(path, 'wb')
+for pattern in patterns:
+    count = int(pattern[0:-1])
+    char = pattern[-1] + '\n'
+    fp.write(char*count)
+fp.close()
+EOF
+
+echo % prepare repo
+hg init a
+cd a
+
+# These initial lines of Xs were not in the original file used to generate
+# the patch.  So all the patch hunks need to be applied to a constant offset
+# within this file.  If the offset isn't tracked then the hunks can be
+# applied to the wrong lines of this file.
+python ../writepatterns.py a 34X 10A 1B 10A 1C 10A 1B 10A 1D 10A 1B 10A 1E 10A 1B 10A
+hg commit -Am adda
+
+# This is a cleaner patch generated via diff
+# In this case it reproduces the problem when
+# the output of hg export does not
+echo % import patch
+hg import -v -m 'b' -d '2 0' - <<EOF
+--- a/a	2009-12-08 19:26:17.000000000 -0800
++++ b/a	2009-12-08 19:26:17.000000000 -0800
+@@ -9,7 +9,7 @@
+ A
+ A
+ B
+-A
++a
+ A
+ A
+ A
+@@ -53,7 +53,7 @@
+ A
+ A
+ B
+-A
++a
+ A
+ A
+ A
+@@ -75,7 +75,7 @@
+ A
+ A
+ B
+-A
++a
+ A
+ A
+ A
+EOF
+
+echo % compare imported changes against reference file
+python ../writepatterns.py aref 34X 10A 1B 1a 9A 1C 10A 1B 10A 1D 10A 1B 1a 9A 1E 10A 1B 1a 9A
+diff -u aref a
+

tests/test-patch-offset.out

@@ -0,0 +1,10 b''
+% prepare repo
+adding a
+% import patch
+applying patch from stdin
+patching file a
+Hunk #1 succeeded at 43 (offset 34 lines).
+Hunk #2 succeeded at 87 (offset 34 lines).
+Hunk #3 succeeded at 109 (offset 34 lines).
+a
+% compare imported changes against reference file

mercurial/patch.py

@@ -1,1430 +1,1435 b''
 # patch.py - patch file parsing routines
 #
 # Copyright 2006 Brendan Cully <[e-mail]>
 # Copyright 2007 Chris Mason <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2, incorporated herein by reference.
 
 from i18n import _
 from node import hex, nullid, short
 import base85, cmdutil, mdiff, util, diffhelpers, copies
 import cStringIO, email.Parser, os, re
 import sys, tempfile, zlib
 
 gitre = re.compile('diff --git a/(.*) b/(.*)')
 
 class PatchError(Exception):
     pass
 
 class NoHunks(PatchError):
     pass
 
 # helper functions
 
 def copyfile(src, dst, basedir):
     abssrc, absdst = [util.canonpath(basedir, basedir, x) for x in [src, dst]]
     if os.path.exists(absdst):
         raise util.Abort(_("cannot create %s: destination already exists") %
                          dst)
 
     dstdir = os.path.dirname(absdst)
     if dstdir and not os.path.isdir(dstdir):
         try:
             os.makedirs(dstdir)
         except IOError:
             raise util.Abort(
                 _("cannot create %s: unable to create destination directory")
                 % dst)
 
     util.copyfile(abssrc, absdst)
 
 # public functions
 
 def extract(ui, fileobj):
     '''extract patch from data read from fileobj.
 
     patch can be a normal patch or contained in an email message.
 
     return tuple (filename, message, user, date, node, p1, p2).
     Any item in the returned tuple can be None. If filename is None,
     fileobj did not contain a patch. Caller must unlink filename when done.'''
 
     # attempt to detect the start of a patch
     # (this heuristic is borrowed from quilt)
     diffre = re.compile(r'^(?:Index:[ \t]|diff[ \t]|RCS file: |'
                         r'retrieving revision [0-9]+(\.[0-9]+)*$|'
                         r'(---|\*\*\*)[ \t])', re.MULTILINE)
 
     fd, tmpname = tempfile.mkstemp(prefix='hg-patch-')
     tmpfp = os.fdopen(fd, 'w')
     try:
         msg = email.Parser.Parser().parse(fileobj)
 
         subject = msg['Subject']
         user = msg['From']
         if not subject and not user:
             # Not an email, restore parsed headers if any
             subject = '\n'.join(': '.join(h) for h in msg.items()) + '\n'
 
         gitsendmail = 'git-send-email' in msg.get('X-Mailer', '')
         # should try to parse msg['Date']
         date = None
         nodeid = None
         branch = None
         parents = []
 
         if subject:
             if subject.startswith('[PATCH'):
                 pend = subject.find(']')
                 if pend >= 0:
                     subject = subject[pend+1:].lstrip()
             subject = subject.replace('\n\t', ' ')
             ui.debug('Subject: %s\n' % subject)
         if user:
             ui.debug('From: %s\n' % user)
         diffs_seen = 0
         ok_types = ('text/plain', 'text/x-diff', 'text/x-patch')
         message = ''
         for part in msg.walk():
             content_type = part.get_content_type()
             ui.debug('Content-Type: %s\n' % content_type)
             if content_type not in ok_types:
                 continue
             payload = part.get_payload(decode=True)
             m = diffre.search(payload)
             if m:
                 hgpatch = False
                 ignoretext = False
 
                 ui.debug('found patch at byte %d\n' % m.start(0))
                 diffs_seen += 1
                 cfp = cStringIO.StringIO()
                 for line in payload[:m.start(0)].splitlines():
                     if line.startswith('# HG changeset patch'):
                         ui.debug('patch generated by hg export\n')
                         hgpatch = True
                         # drop earlier commit message content
                         cfp.seek(0)
                         cfp.truncate()
                         subject = None
                     elif hgpatch:
                         if line.startswith('# User '):
                             user = line[7:]
                             ui.debug('From: %s\n' % user)
                         elif line.startswith("# Date "):
                             date = line[7:]
                         elif line.startswith("# Branch "):
                             branch = line[9:]
                         elif line.startswith("# Node ID "):
                             nodeid = line[10:]
                         elif line.startswith("# Parent "):
                             parents.append(line[10:])
                     elif line == '---' and gitsendmail:
                         ignoretext = True
                     if not line.startswith('# ') and not ignoretext:
                         cfp.write(line)
                         cfp.write('\n')
                 message = cfp.getvalue()
                 if tmpfp:
                     tmpfp.write(payload)
                     if not payload.endswith('\n'):
                         tmpfp.write('\n')
             elif not diffs_seen and message and content_type == 'text/plain':
                 message += '\n' + payload
     except:
         tmpfp.close()
         os.unlink(tmpname)
         raise
 
     if subject and not message.startswith(subject):
         message = '%s\n%s' % (subject, message)
     tmpfp.close()
     if not diffs_seen:
         os.unlink(tmpname)
         return None, message, user, date, branch, None, None, None
     p1 = parents and parents.pop(0) or None
     p2 = parents and parents.pop(0) or None
     return tmpname, message, user, date, branch, nodeid, p1, p2
 
 GP_PATCH  = 1 << 0  # we have to run patch
 GP_FILTER = 1 << 1  # there's some copy/rename operation
 GP_BINARY = 1 << 2  # there's a binary patch
 
 class patchmeta(object):
     """Patched file metadata
 
     'op' is the performed operation within ADD, DELETE, RENAME, MODIFY
     or COPY.  'path' is patched file path. 'oldpath' is set to the
     origin file when 'op' is either COPY or RENAME, None otherwise. If
     file mode is changed, 'mode' is a tuple (islink, isexec) where
     'islink' is True if the file is a symlink and 'isexec' is True if
     the file is executable. Otherwise, 'mode' is None.
     """
     def __init__(self, path):
         self.path = path
         self.oldpath = None
         self.mode = None
         self.op = 'MODIFY'
         self.lineno = 0
         self.binary = False
 
     def setmode(self, mode):
         islink = mode & 020000
         isexec = mode & 0100
         self.mode = (islink, isexec)
 
 def readgitpatch(lr):
     """extract git-style metadata about patches from <patchname>"""
 
     # Filter patch for git information
     gp = None
     gitpatches = []
     # Can have a git patch with only metadata, causing patch to complain
     dopatch = 0
 
     lineno = 0
     for line in lr:
         lineno += 1
         line = line.rstrip(' \r\n')
         if line.startswith('diff --git'):
             m = gitre.match(line)
             if m:
                 if gp:
                     gitpatches.append(gp)
                 dst = m.group(2)
                 gp = patchmeta(dst)
                 gp.lineno = lineno
         elif gp:
             if line.startswith('--- '):
                 if gp.op in ('COPY', 'RENAME'):
                     dopatch |= GP_FILTER
                 gitpatches.append(gp)
                 gp = None
                 dopatch |= GP_PATCH
                 continue
             if line.startswith('rename from '):
                 gp.op = 'RENAME'
                 gp.oldpath = line[12:]
             elif line.startswith('rename to '):
                 gp.path = line[10:]
             elif line.startswith('copy from '):
                 gp.op = 'COPY'
                 gp.oldpath = line[10:]
             elif line.startswith('copy to '):
                 gp.path = line[8:]
             elif line.startswith('deleted file'):
                 gp.op = 'DELETE'
                 # is the deleted file a symlink?
                 gp.setmode(int(line[-6:], 8))
             elif line.startswith('new file mode '):
                 gp.op = 'ADD'
                 gp.setmode(int(line[-6:], 8))
             elif line.startswith('new mode '):
                 gp.setmode(int(line[-6:], 8))
             elif line.startswith('GIT binary patch'):
                 dopatch |= GP_BINARY
                 gp.binary = True
     if gp:
         gitpatches.append(gp)
 
     if not gitpatches:
         dopatch = GP_PATCH
 
     return (dopatch, gitpatches)
 
 class linereader(object):
     # simple class to allow pushing lines back into the input stream
     def __init__(self, fp, textmode=False):
         self.fp = fp
         self.buf = []
         self.textmode = textmode
 
     def push(self, line):
         if line is not None:
             self.buf.append(line)
 
     def readline(self):
         if self.buf:
             l = self.buf[0]
             del self.buf[0]
             return l
         l = self.fp.readline()
         if self.textmode and l.endswith('\r\n'):
             l = l[:-2] + '\n'
         return l
 
     def __iter__(self):
         while 1:
             l = self.readline()
             if not l:
                 break
             yield l
 
 # @@ -start,len +start,len @@ or @@ -start +start @@ if len is 1
 unidesc = re.compile('@@ -(\d+)(,(\d+))? \+(\d+)(,(\d+))? @@')
 contextdesc = re.compile('(---|\*\*\*) (\d+)(,(\d+))? (---|\*\*\*)')
 
 class patchfile(object):
     def __init__(self, ui, fname, opener, missing=False, eol=None):
         self.fname = fname
         self.eol = eol
         self.opener = opener
         self.ui = ui
         self.lines = []
         self.exists = False
         self.missing = missing
         if not missing:
             try:
                 self.lines = self.readlines(fname)
                 self.exists = True
             except IOError:
                 pass
         else:
             self.ui.warn(_("unable to find '%s' for patching\n") % self.fname)
 
         self.hash = {}
         self.dirty = 0
         self.offset = 0
+        self.skew = 0
         self.rej = []
         self.fileprinted = False
         self.printfile(False)
         self.hunks = 0
 
     def readlines(self, fname):
         if os.path.islink(fname):
             return [os.readlink(fname)]
         fp = self.opener(fname, 'r')
         try:
             return list(linereader(fp, self.eol is not None))
         finally:
             fp.close()
 
     def writelines(self, fname, lines):
         # Ensure supplied data ends in fname, being a regular file or
         # a symlink. updatedir() will -too magically- take care of
         # setting it to the proper type afterwards.
         islink = os.path.islink(fname)
         if islink:
             fp = cStringIO.StringIO()
         else:
             fp = self.opener(fname, 'w')
         try:
             if self.eol and self.eol != '\n':
                 for l in lines:
                     if l and l[-1] == '\n':
                         l = l[:-1] + self.eol
                     fp.write(l)
             else:
                 fp.writelines(lines)
             if islink:
                 self.opener.symlink(fp.getvalue(), fname)
         finally:
             fp.close()
 
     def unlink(self, fname):
         os.unlink(fname)
 
     def printfile(self, warn):
         if self.fileprinted:
             return
         if warn or self.ui.verbose:
             self.fileprinted = True
         s = _("patching file %s\n") % self.fname
         if warn:
             self.ui.warn(s)
         else:
             self.ui.note(s)
 
 
     def findlines(self, l, linenum):
         # looks through the hash and finds candidate lines.  The
         # result is a list of line numbers sorted based on distance
         # from linenum
 
         cand = self.hash.get(l, [])
         if len(cand) > 1:
             # resort our list of potentials forward then back.
             cand.sort(key=lambda x: abs(x - linenum))
         return cand
 
     def hashlines(self):
         self.hash = {}
         for x, s in enumerate(self.lines):
             self.hash.setdefault(s, []).append(x)
 
     def write_rej(self):
         # our rejects are a little different from patch(1).  This always
         # creates rejects in the same form as the original patch.  A file
         # header is inserted so that you can run the reject through patch again
         # without having to type the filename.
 
         if not self.rej:
             return
 
         fname = self.fname + ".rej"
         self.ui.warn(
             _("%d out of %d hunks FAILED -- saving rejects to file %s\n") %
             (len(self.rej), self.hunks, fname))
 
         def rejlines():
             base = os.path.basename(self.fname)
             yield "--- %s\n+++ %s\n" % (base, base)
             for x in self.rej:
                 for l in x.hunk:
                     yield l
                     if l[-1] != '\n':
                         yield "\n\ No newline at end of file\n"
 
         self.writelines(fname, rejlines())
 
     def write(self, dest=None):
         if not self.dirty:
             return
         if not dest:
             dest = self.fname
         self.writelines(dest, self.lines)
 
     def close(self):
         self.write()
         self.write_rej()
 
     def apply(self, h):
         if not h.complete():
             raise PatchError(_("bad hunk #%d %s (%d %d %d %d)") %
                             (h.number, h.desc, len(h.a), h.lena, len(h.b),
                             h.lenb))
 
         self.hunks += 1
 
         if self.missing:
             self.rej.append(h)
             return -1
 
         if self.exists and h.createfile():
             self.ui.warn(_("file %s already exists\n") % self.fname)
             self.rej.append(h)
             return -1
 
         if isinstance(h, binhunk):
             if h.rmfile():
                 self.unlink(self.fname)
             else:
                 self.lines[:] = h.new()
                 self.offset += len(h.new())
                 self.dirty = 1
             return 0
 
         # fast case first, no offsets, no fuzz
         old = h.old()
         # patch starts counting at 1 unless we are adding the file
         if h.starta == 0:
             start = 0
         else:
             start = h.starta + self.offset - 1
         orig_start = start
-        if diffhelpers.testhunk(old, self.lines, start) == 0:
+        # if there's skew we want to emit the "(offset %d lines)" even
+        # when the hunk cleanly applies at start + skew, so skip the
+        # fast case code
+        if self.skew == 0 and diffhelpers.testhunk(old, self.lines, start) == 0:
             if h.rmfile():
                 self.unlink(self.fname)
             else:
                 self.lines[start : start + h.lena] = h.new()
                 self.offset += h.lenb - h.lena
                 self.dirty = 1
             return 0
 
         # ok, we couldn't match the hunk.  Lets look for offsets and fuzz it
         self.hashlines()
         if h.hunk[-1][0] != ' ':
             # if the hunk tried to put something at the bottom of the file
             # override the start line and use eof here
             search_start = len(self.lines)
         else:
-            search_start = orig_start
+            search_start = orig_start + self.skew
 
         for fuzzlen in xrange(3):
             for toponly in [ True, False ]:
                 old = h.old(fuzzlen, toponly)
 
                 cand = self.findlines(old[0][1:], search_start)
                 for l in cand:
                     if diffhelpers.testhunk(old, self.lines, l) == 0:
                         newlines = h.new(fuzzlen, toponly)
                         self.lines[l : l + len(old)] = newlines
                         self.offset += len(newlines) - len(old)
+                        self.skew = l - orig_start
                         self.dirty = 1
                         if fuzzlen:
                             fuzzstr = "with fuzz %d " % fuzzlen
                             f = self.ui.warn
                             self.printfile(True)
                         else:
                             fuzzstr = ""
                             f = self.ui.note
                         offset = l - orig_start - fuzzlen
                         if offset == 1:
                             msg = _("Hunk #%d succeeded at %d %s"
                                     "(offset %d line).\n")
                         else:
                             msg = _("Hunk #%d succeeded at %d %s"
                                     "(offset %d lines).\n")
                         f(msg % (h.number, l+1, fuzzstr, offset))
                         return fuzzlen
         self.printfile(True)
         self.ui.warn(_("Hunk #%d FAILED at %d\n") % (h.number, orig_start))
         self.rej.append(h)
         return -1
 
 class hunk(object):
     def __init__(self, desc, num, lr, context, create=False, remove=False):
         self.number = num
         self.desc = desc
         self.hunk = [ desc ]
         self.a = []
         self.b = []
         self.starta = self.lena = None
         self.startb = self.lenb = None
         if context:
             self.read_context_hunk(lr)
         else:
             self.read_unified_hunk(lr)
         self.create = create
         self.remove = remove and not create
 
     def read_unified_hunk(self, lr):
         m = unidesc.match(self.desc)
         if not m:
             raise PatchError(_("bad hunk #%d") % self.number)
         self.starta, foo, self.lena, self.startb, foo2, self.lenb = m.groups()
         if self.lena is None:
             self.lena = 1
         else:
             self.lena = int(self.lena)
         if self.lenb is None:
             self.lenb = 1
         else:
             self.lenb = int(self.lenb)
         self.starta = int(self.starta)
         self.startb = int(self.startb)
         diffhelpers.addlines(lr, self.hunk, self.lena, self.lenb, self.a, self.b)
         # if we hit eof before finishing out the hunk, the last line will
         # be zero length.  Lets try to fix it up.
         while len(self.hunk[-1]) == 0:
             del self.hunk[-1]
             del self.a[-1]
             del self.b[-1]
             self.lena -= 1
             self.lenb -= 1
 
     def read_context_hunk(self, lr):
         self.desc = lr.readline()
         m = contextdesc.match(self.desc)
         if not m:
             raise PatchError(_("bad hunk #%d") % self.number)
         foo, self.starta, foo2, aend, foo3 = m.groups()
         self.starta = int(self.starta)
         if aend is None:
             aend = self.starta
         self.lena = int(aend) - self.starta
         if self.starta:
             self.lena += 1
         for x in xrange(self.lena):
             l = lr.readline()
             if l.startswith('---'):
                 lr.push(l)
                 break
             s = l[2:]
             if l.startswith('- ') or l.startswith('! '):
                 u = '-' + s
             elif l.startswith('  '):
                 u = ' ' + s
             else:
                 raise PatchError(_("bad hunk #%d old text line %d") %
                                  (self.number, x))
             self.a.append(u)
             self.hunk.append(u)
 
         l = lr.readline()
         if l.startswith('\ '):
             s = self.a[-1][:-1]
             self.a[-1] = s
             self.hunk[-1] = s
             l = lr.readline()
         m = contextdesc.match(l)
         if not m:
             raise PatchError(_("bad hunk #%d") % self.number)
         foo, self.startb, foo2, bend, foo3 = m.groups()
         self.startb = int(self.startb)
         if bend is None:
             bend = self.startb
         self.lenb = int(bend) - self.startb
         if self.startb:
             self.lenb += 1
         hunki = 1
         for x in xrange(self.lenb):
             l = lr.readline()
             if l.startswith('\ '):
                 s = self.b[-1][:-1]
                 self.b[-1] = s
                 self.hunk[hunki-1] = s
                 continue
             if not l:
                 lr.push(l)
                 break
             s = l[2:]
             if l.startswith('+ ') or l.startswith('! '):
                 u = '+' + s
             elif l.startswith('  '):
                 u = ' ' + s
             elif len(self.b) == 0:
                 # this can happen when the hunk does not add any lines
                 lr.push(l)
                 break
             else:
                 raise PatchError(_("bad hunk #%d old text line %d") %
                                  (self.number, x))
             self.b.append(s)
             while True:
                 if hunki >= len(self.hunk):
                     h = ""
                 else:
                     h = self.hunk[hunki]
                 hunki += 1
                 if h == u:
                     break
                 elif h.startswith('-'):
                     continue
                 else:
                     self.hunk.insert(hunki-1, u)
                     break
 
         if not self.a:
             # this happens when lines were only added to the hunk
             for x in self.hunk:
                 if x.startswith('-') or x.startswith(' '):
                     self.a.append(x)
         if not self.b:
             # this happens when lines were only deleted from the hunk
             for x in self.hunk:
                 if x.startswith('+') or x.startswith(' '):
                     self.b.append(x[1:])
         # @@ -start,len +start,len @@
         self.desc = "@@ -%d,%d +%d,%d @@\n" % (self.starta, self.lena,
                                              self.startb, self.lenb)
         self.hunk[0] = self.desc
 
     def fix_newline(self):
         diffhelpers.fix_newline(self.hunk, self.a, self.b)
 
     def complete(self):
         return len(self.a) == self.lena and len(self.b) == self.lenb
 
     def createfile(self):
         return self.starta == 0 and self.lena == 0 and self.create
 
     def rmfile(self):
         return self.startb == 0 and self.lenb == 0 and self.remove
 
     def fuzzit(self, l, fuzz, toponly):
         # this removes context lines from the top and bottom of list 'l'.  It
         # checks the hunk to make sure only context lines are removed, and then
         # returns a new shortened list of lines.
         fuzz = min(fuzz, len(l)-1)
         if fuzz:
             top = 0
             bot = 0
             hlen = len(self.hunk)
             for x in xrange(hlen-1):
                 # the hunk starts with the @@ line, so use x+1
                 if self.hunk[x+1][0] == ' ':
                     top += 1
                 else:
                     break
             if not toponly:
                 for x in xrange(hlen-1):
                     if self.hunk[hlen-bot-1][0] == ' ':
                         bot += 1
                     else:
                         break
 
             # top and bot now count context in the hunk
             # adjust them if either one is short
             context = max(top, bot, 3)
             if bot < context:
                 bot = max(0, fuzz - (context - bot))
             else:
                 bot = min(fuzz, bot)
             if top < context:
                 top = max(0, fuzz - (context - top))
             else:
                 top = min(fuzz, top)
 
             return l[top:len(l)-bot]
         return l
 
     def old(self, fuzz=0, toponly=False):
         return self.fuzzit(self.a, fuzz, toponly)
 
     def newctrl(self):
         res = []
         for x in self.hunk:
             c = x[0]
             if c == ' ' or c == '+':
                 res.append(x)
         return res
 
     def new(self, fuzz=0, toponly=False):
         return self.fuzzit(self.b, fuzz, toponly)
 
 class binhunk:
     'A binary patch file. Only understands literals so far.'
     def __init__(self, gitpatch):
         self.gitpatch = gitpatch
         self.text = None
         self.hunk = ['GIT binary patch\n']
 
     def createfile(self):
         return self.gitpatch.op in ('ADD', 'RENAME', 'COPY')
 
     def rmfile(self):
         return self.gitpatch.op == 'DELETE'
 
     def complete(self):
         return self.text is not None
 
     def new(self):
         return [self.text]
 
     def extract(self, lr):
         line = lr.readline()
         self.hunk.append(line)
         while line and not line.startswith('literal '):
             line = lr.readline()
             self.hunk.append(line)
         if not line:
             raise PatchError(_('could not extract binary patch'))
         size = int(line[8:].rstrip())
         dec = []
         line = lr.readline()
         self.hunk.append(line)
         while len(line) > 1:
             l = line[0]
             if l <= 'Z' and l >= 'A':
                 l = ord(l) - ord('A') + 1
             else:
                 l = ord(l) - ord('a') + 27
             dec.append(base85.b85decode(line[1:-1])[:l])
             line = lr.readline()
             self.hunk.append(line)
         text = zlib.decompress(''.join(dec))
         if len(text) != size:
             raise PatchError(_('binary patch is %d bytes, not %d') %
                              len(text), size)
         self.text = text
 
 def parsefilename(str):
     # --- filename \t|space stuff
     s = str[4:].rstrip('\r\n')
     i = s.find('\t')
     if i < 0:
         i = s.find(' ')
         if i < 0:
             return s
     return s[:i]
 
 def selectfile(afile_orig, bfile_orig, hunk, strip):
     def pathstrip(path, count=1):
         pathlen = len(path)
         i = 0
         if count == 0:
             return '', path.rstrip()
         while count > 0:
             i = path.find('/', i)
             if i == -1:
                 raise PatchError(_("unable to strip away %d dirs from %s") %
                                  (count, path))
             i += 1
             # consume '//' in the path
             while i < pathlen - 1 and path[i] == '/':
                 i += 1
             count -= 1
         return path[:i].lstrip(), path[i:].rstrip()
 
     nulla = afile_orig == "/dev/null"
     nullb = bfile_orig == "/dev/null"
     abase, afile = pathstrip(afile_orig, strip)
     gooda = not nulla and util.lexists(afile)
     bbase, bfile = pathstrip(bfile_orig, strip)
     if afile == bfile:
         goodb = gooda
     else:
         goodb = not nullb and os.path.exists(bfile)
     createfunc = hunk.createfile
     missing = not goodb and not gooda and not createfunc()
 
     # some diff programs apparently produce create patches where the
     # afile is not /dev/null, but rather the same name as the bfile
     if missing and afile == bfile:
         # this isn't very pretty
         hunk.create = True
         if createfunc():
             missing = False
         else:
             hunk.create = False
 
     # If afile is "a/b/foo" and bfile is "a/b/foo.orig" we assume the
     # diff is between a file and its backup. In this case, the original
     # file should be patched (see original mpatch code).
     isbackup = (abase == bbase and bfile.startswith(afile))
     fname = None
     if not missing:
         if gooda and goodb:
             fname = isbackup and afile or bfile
         elif gooda:
             fname = afile
 
     if not fname:
         if not nullb:
             fname = isbackup and afile or bfile
         elif not nulla:
             fname = afile
         else:
             raise PatchError(_("undefined source and destination files"))
 
     return fname, missing
 
 def scangitpatch(lr, firstline):
     """
     Git patches can emit:
     - rename a to b
     - change b
     - copy a to c
     - change c
 
     We cannot apply this sequence as-is, the renamed 'a' could not be
     found for it would have been renamed already. And we cannot copy
     from 'b' instead because 'b' would have been changed already. So
     we scan the git patch for copy and rename commands so we can
     perform the copies ahead of time.
     """
     pos = 0
     try:
         pos = lr.fp.tell()
         fp = lr.fp
     except IOError:
         fp = cStringIO.StringIO(lr.fp.read())
     gitlr = linereader(fp, lr.textmode)
     gitlr.push(firstline)
     (dopatch, gitpatches) = readgitpatch(gitlr)
     fp.seek(pos)
     return dopatch, gitpatches
 
 def iterhunks(ui, fp, sourcefile=None, textmode=False):
     """Read a patch and yield the following events:
     - ("file", afile, bfile, firsthunk): select a new target file.
     - ("hunk", hunk): a new hunk is ready to be applied, follows a
     "file" event.
     - ("git", gitchanges): current diff is in git format, gitchanges
     maps filenames to gitpatch records. Unique event.
 
     If textmode is True, input line-endings are normalized to LF.
     """
     changed = {}
     current_hunk = None
     afile = ""
     bfile = ""
     state = None
     hunknum = 0
     emitfile = False
     git = False
 
     # our states
     BFILE = 1
     context = None
     lr = linereader(fp, textmode)
     dopatch = True
     # gitworkdone is True if a git operation (copy, rename, ...) was
     # performed already for the current file. Useful when the file
     # section may have no hunk.
     gitworkdone = False
 
     while True:
         newfile = False
         x = lr.readline()
         if not x:
             break
         if current_hunk:
             if x.startswith('\ '):
                 current_hunk.fix_newline()
             yield 'hunk', current_hunk
             current_hunk = None
             gitworkdone = False
         if ((sourcefile or state == BFILE) and ((not context and x[0] == '@') or
             ((context is not False) and x.startswith('***************')))):
             try:
                 if context is None and x.startswith('***************'):
                     context = True
                 gpatch = changed.get(bfile)
                 create = afile == '/dev/null' or gpatch and gpatch.op == 'ADD'
                 remove = bfile == '/dev/null' or gpatch and gpatch.op == 'DELETE'
                 current_hunk = hunk(x, hunknum + 1, lr, context, create, remove)
             except PatchError, err:
                 ui.debug(err)
                 current_hunk = None
                 continue
             hunknum += 1
             if emitfile:
                 emitfile = False
                 yield 'file', (afile, bfile, current_hunk)
         elif state == BFILE and x.startswith('GIT binary patch'):
             current_hunk = binhunk(changed[bfile])
             hunknum += 1
             if emitfile:
                 emitfile = False
                 yield 'file', ('a/' + afile, 'b/' + bfile, current_hunk)
             current_hunk.extract(lr)
         elif x.startswith('diff --git'):
             # check for git diff, scanning the whole patch file if needed
             m = gitre.match(x)
             if m:
                 afile, bfile = m.group(1, 2)
                 if not git:
                     git = True
                     dopatch, gitpatches = scangitpatch(lr, x)
                     yield 'git', gitpatches
                     for gp in gitpatches:
                         changed[gp.path] = gp
                 # else error?
                 # copy/rename + modify should modify target, not source
                 gp = changed.get(bfile)
                 if gp and gp.op in ('COPY', 'DELETE', 'RENAME', 'ADD'):
                     afile = bfile
                     gitworkdone = True
             newfile = True
         elif x.startswith('---'):
             # check for a unified diff
             l2 = lr.readline()
             if not l2.startswith('+++'):
                 lr.push(l2)
                 continue
             newfile = True
             context = False
             afile = parsefilename(x)
             bfile = parsefilename(l2)
         elif x.startswith('***'):
             # check for a context diff
             l2 = lr.readline()
             if not l2.startswith('---'):
                 lr.push(l2)
                 continue
             l3 = lr.readline()
             lr.push(l3)
             if not l3.startswith("***************"):
                 lr.push(l2)
                 continue
             newfile = True
             context = True
             afile = parsefilename(x)
             bfile = parsefilename(l2)
 
         if newfile:
             emitfile = True
             state = BFILE
             hunknum = 0
     if current_hunk:
         if current_hunk.complete():
             yield 'hunk', current_hunk
         else:
             raise PatchError(_("malformed patch %s %s") % (afile,
                              current_hunk.desc))
 
     if hunknum == 0 and dopatch and not gitworkdone:
         raise NoHunks
 
 def applydiff(ui, fp, changed, strip=1, sourcefile=None, eol=None):
     """
     Reads a patch from fp and tries to apply it.
 
     The dict 'changed' is filled in with all of the filenames changed
     by the patch. Returns 0 for a clean patch, -1 if any rejects were
     found and 1 if there was any fuzz.
 
     If 'eol' is None, the patch content and patched file are read in
     binary mode. Otherwise, line endings are ignored when patching then
     normalized to 'eol' (usually '\n' or \r\n').
     """
     rejects = 0
     err = 0
     current_file = None
     gitpatches = None
     opener = util.opener(os.getcwd())
     textmode = eol is not None
 
     def closefile():
         if not current_file:
             return 0
         current_file.close()
         return len(current_file.rej)
 
     for state, values in iterhunks(ui, fp, sourcefile, textmode):
         if state == 'hunk':
             if not current_file:
                 continue
             current_hunk = values
             ret = current_file.apply(current_hunk)
             if ret >= 0:
                 changed.setdefault(current_file.fname, None)
                 if ret > 0:
                     err = 1
         elif state == 'file':
             rejects += closefile()
             afile, bfile, first_hunk = values
             try:
                 if sourcefile:
                     current_file = patchfile(ui, sourcefile, opener, eol=eol)
                 else:
                     current_file, missing = selectfile(afile, bfile, first_hunk,
                                             strip)
                     current_file = patchfile(ui, current_file, opener, missing, eol)
             except PatchError, err:
                 ui.warn(str(err) + '\n')
                 current_file, current_hunk = None, None
                 rejects += 1
                 continue
         elif state == 'git':
             gitpatches = values
             cwd = os.getcwd()
             for gp in gitpatches:
                 if gp.op in ('COPY', 'RENAME'):
                     copyfile(gp.oldpath, gp.path, cwd)
                 changed[gp.path] = gp
         else:
             raise util.Abort(_('unsupported parser state: %s') % state)
 
     rejects += closefile()
 
     if rejects:
         return -1
     return err
 
 def diffopts(ui, opts=None, untrusted=False):
     def get(key, name=None, getter=ui.configbool):
         return ((opts and opts.get(key)) or
                 getter('diff', name or key, None, untrusted=untrusted))
     return mdiff.diffopts(
         text=opts and opts.get('text'),
         git=get('git'),
         nodates=get('nodates'),
         showfunc=get('show_function', 'showfunc'),
         ignorews=get('ignore_all_space', 'ignorews'),
         ignorewsamount=get('ignore_space_change', 'ignorewsamount'),
         ignoreblanklines=get('ignore_blank_lines', 'ignoreblanklines'),
         context=get('unified', getter=ui.config))
 
 def updatedir(ui, repo, patches, similarity=0):
     '''Update dirstate after patch application according to metadata'''
     if not patches:
         return
     copies = []
     removes = set()
     cfiles = patches.keys()
     cwd = repo.getcwd()
     if cwd:
         cfiles = [util.pathto(repo.root, cwd, f) for f in patches.keys()]
     for f in patches:
         gp = patches[f]
         if not gp:
             continue
         if gp.op == 'RENAME':
             copies.append((gp.oldpath, gp.path))
             removes.add(gp.oldpath)
         elif gp.op == 'COPY':
             copies.append((gp.oldpath, gp.path))
         elif gp.op == 'DELETE':
             removes.add(gp.path)
     for src, dst in copies:
         repo.copy(src, dst)
     if (not similarity) and removes:
         repo.remove(sorted(removes), True)
     for f in patches:
         gp = patches[f]
         if gp and gp.mode:
             islink, isexec = gp.mode
             dst = repo.wjoin(gp.path)
             # patch won't create empty files
             if gp.op == 'ADD' and not os.path.exists(dst):
                 flags = (isexec and 'x' or '') + (islink and 'l' or '')
                 repo.wwrite(gp.path, '', flags)
             elif gp.op != 'DELETE':
                 util.set_flags(dst, islink, isexec)
     cmdutil.addremove(repo, cfiles, similarity=similarity)
     files = patches.keys()
     files.extend([r for r in removes if r not in files])
     return sorted(files)
 
 def externalpatch(patcher, args, patchname, ui, strip, cwd, files):
     """use <patcher> to apply <patchname> to the working directory.
     returns whether patch was applied with fuzz factor."""
 
     fuzz = False
     if cwd:
         args.append('-d %s' % util.shellquote(cwd))
     fp = util.popen('%s %s -p%d < %s' % (patcher, ' '.join(args), strip,
                                        util.shellquote(patchname)))
 
     for line in fp:
         line = line.rstrip()
         ui.note(line + '\n')
         if line.startswith('patching file '):
             pf = util.parse_patch_output(line)
             printed_file = False
             files.setdefault(pf, None)
         elif line.find('with fuzz') >= 0:
             fuzz = True
             if not printed_file:
                 ui.warn(pf + '\n')
                 printed_file = True
             ui.warn(line + '\n')
         elif line.find('saving rejects to file') >= 0:
             ui.warn(line + '\n')
         elif line.find('FAILED') >= 0:
             if not printed_file:
                 ui.warn(pf + '\n')
                 printed_file = True
             ui.warn(line + '\n')
     code = fp.close()
     if code:
         raise PatchError(_("patch command failed: %s") %
                          util.explain_exit(code)[0])
     return fuzz
 
 def internalpatch(patchobj, ui, strip, cwd, files=None, eolmode='strict'):
     """use builtin patch to apply <patchobj> to the working directory.
     returns whether patch was applied with fuzz factor."""
 
     if files is None:
         files = {}
     if eolmode is None:
         eolmode = ui.config('patch', 'eol', 'strict')
     try:
         eol = {'strict': None, 'crlf': '\r\n', 'lf': '\n'}[eolmode.lower()]
     except KeyError:
         raise util.Abort(_('Unsupported line endings type: %s') % eolmode)
 
     try:
         fp = open(patchobj, 'rb')
     except TypeError:
         fp = patchobj
     if cwd:
         curdir = os.getcwd()
         os.chdir(cwd)
     try:
         ret = applydiff(ui, fp, files, strip=strip, eol=eol)
     finally:
         if cwd:
             os.chdir(curdir)
     if ret < 0:
         raise PatchError
     return ret > 0
 
 def patch(patchname, ui, strip=1, cwd=None, files=None, eolmode='strict'):
     """Apply <patchname> to the working directory.
 
     'eolmode' specifies how end of lines should be handled. It can be:
     - 'strict': inputs are read in binary mode, EOLs are preserved
     - 'crlf': EOLs are ignored when patching and reset to CRLF
     - 'lf': EOLs are ignored when patching and reset to LF
     - None: get it from user settings, default to 'strict'
     'eolmode' is ignored when using an external patcher program.
 
     Returns whether patch was applied with fuzz factor.
     """
     patcher = ui.config('ui', 'patch')
     args = []
     if files is None:
         files = {}
     try:
         if patcher:
             return externalpatch(patcher, args, patchname, ui, strip, cwd,
                                  files)
         else:
             try:
                 return internalpatch(patchname, ui, strip, cwd, files, eolmode)
             except NoHunks:
                 patcher = util.find_exe('gpatch') or util.find_exe('patch') or 'patch'
                 ui.debug('no valid hunks found; trying with %r instead\n' %
                          patcher)
                 if util.needbinarypatch():
                     args.append('--binary')
                 return externalpatch(patcher, args, patchname, ui, strip, cwd,
                                      files)
     except PatchError, err:
         s = str(err)
         if s:
             raise util.Abort(s)
         else:
             raise util.Abort(_('patch failed to apply'))
 
 def b85diff(to, tn):
     '''print base85-encoded binary diff'''
     def gitindex(text):
         if not text:
             return '0' * 40
         l = len(text)
         s = util.sha1('blob %d\0' % l)
         s.update(text)
         return s.hexdigest()
 
     def fmtline(line):
         l = len(line)
         if l <= 26:
             l = chr(ord('A') + l - 1)
         else:
             l = chr(l - 26 + ord('a') - 1)
         return '%c%s\n' % (l, base85.b85encode(line, True))
 
     def chunk(text, csize=52):
         l = len(text)
         i = 0
         while i < l:
             yield text[i:i+csize]
             i += csize
 
     tohash = gitindex(to)
     tnhash = gitindex(tn)
     if tohash == tnhash:
         return ""
 
     # TODO: deltas
     ret = ['index %s..%s\nGIT binary patch\nliteral %s\n' %
            (tohash, tnhash, len(tn))]
     for l in chunk(zlib.compress(tn)):
         ret.append(fmtline(l))
     ret.append('\n')
     return ''.join(ret)
 
 def _addmodehdr(header, omode, nmode):
     if omode != nmode:
         header.append('old mode %s\n' % omode)
         header.append('new mode %s\n' % nmode)
 
 def diff(repo, node1=None, node2=None, match=None, changes=None, opts=None):
     '''yields diff of changes to files between two nodes, or node and
     working directory.
 
     if node1 is None, use first dirstate parent instead.
     if node2 is None, compare node1 with working directory.'''
 
     if opts is None:
         opts = mdiff.defaultopts
 
     if not node1 and not node2:
         node1 = repo.dirstate.parents()[0]
 
     def lrugetfilectx():
         cache = {}
         order = []
         def getfilectx(f, ctx):
             fctx = ctx.filectx(f, filelog=cache.get(f))
             if f not in cache:
                 if len(cache) > 20:
                     del cache[order.pop(0)]
                 cache[f] = fctx.filelog()
             else:
                 order.remove(f)
             order.append(f)
             return fctx
         return getfilectx
     getfilectx = lrugetfilectx()
 
     ctx1 = repo[node1]
     ctx2 = repo[node2]
 
     if not changes:
         changes = repo.status(ctx1, ctx2, match=match)
     modified, added, removed = changes[:3]
 
     if not modified and not added and not removed:
         return
 
     date1 = util.datestr(ctx1.date())
     man1 = ctx1.manifest()
 
     if repo.ui.quiet:
         r = None
     else:
         hexfunc = repo.ui.debugflag and hex or short
         r = [hexfunc(node) for node in [node1, node2] if node]
 
     if opts.git:
         copy, diverge = copies.copies(repo, ctx1, ctx2, repo[nullid])
         copy = copy.copy()
         for k, v in copy.items():
             copy[v] = k
 
     gone = set()
     gitmode = {'l': '120000', 'x': '100755', '': '100644'}
 
     for f in sorted(modified + added + removed):
         to = None
         tn = None
         dodiff = True
         header = []
         if f in man1:
             to = getfilectx(f, ctx1).data()
         if f not in removed:
             tn = getfilectx(f, ctx2).data()
         a, b = f, f
         if opts.git:
             if f in added:
                 mode = gitmode[ctx2.flags(f)]
                 if f in copy:
                     a = copy[f]
                     omode = gitmode[man1.flags(a)]
                     _addmodehdr(header, omode, mode)
                     if a in removed and a not in gone:
                         op = 'rename'
                         gone.add(a)
                     else:
                         op = 'copy'
                     header.append('%s from %s\n' % (op, a))
                     header.append('%s to %s\n' % (op, f))
                     to = getfilectx(a, ctx1).data()
                 else:
                     header.append('new file mode %s\n' % mode)
                 if util.binary(tn):
                     dodiff = 'binary'
             elif f in removed:
                 # have we already reported a copy above?
                 if f in copy and copy[f] in added and copy[copy[f]] == f:
                     dodiff = False
                 else:
                     header.append('deleted file mode %s\n' %
                                   gitmode[man1.flags(f)])
             else:
                 omode = gitmode[man1.flags(f)]
                 nmode = gitmode[ctx2.flags(f)]
                 _addmodehdr(header, omode, nmode)
                 if util.binary(to) or util.binary(tn):
                     dodiff = 'binary'
             r = None
             header.insert(0, mdiff.diffline(r, a, b, opts))
         if dodiff:
             if dodiff == 'binary':
                 text = b85diff(to, tn)
             else:
                 text = mdiff.unidiff(to, date1,
                                     # ctx2 date may be dynamic
                                     tn, util.datestr(ctx2.date()),
                                     a, b, r, opts=opts)
             if header and (text or len(header) > 1):
                 yield ''.join(header)
             if text:
                 yield text
 
 def export(repo, revs, template='hg-%h.patch', fp=None, switch_parent=False,
            opts=None):
     '''export changesets as hg patches.'''
 
     total = len(revs)
     revwidth = max([len(str(rev)) for rev in revs])
 
     def single(rev, seqno, fp):
         ctx = repo[rev]
         node = ctx.node()
         parents = [p.node() for p in ctx.parents() if p]
         branch = ctx.branch()
         if switch_parent:
             parents.reverse()
         prev = (parents and parents[0]) or nullid
 
         if not fp:
             fp = cmdutil.make_file(repo, template, node, total=total,
                                    seqno=seqno, revwidth=revwidth,
                                    mode='ab')
         if fp != sys.stdout and hasattr(fp, 'name'):
             repo.ui.note("%s\n" % fp.name)
 
         fp.write("# HG changeset patch\n")
         fp.write("# User %s\n" % ctx.user())
         fp.write("# Date %d %d\n" % ctx.date())
         if branch and (branch != 'default'):
             fp.write("# Branch %s\n" % branch)
         fp.write("# Node ID %s\n" % hex(node))
         fp.write("# Parent  %s\n" % hex(prev))
         if len(parents) > 1:
             fp.write("# Parent  %s\n" % hex(parents[1]))
         fp.write(ctx.description().rstrip())
         fp.write("\n\n")
 
         for chunk in diff(repo, prev, node, opts=opts):
             fp.write(chunk)
 
     for seqno, rev in enumerate(revs):
         single(rev, seqno+1, fp)
 
 def diffstatdata(lines):
     filename, adds, removes = None, 0, 0
     for line in lines:
         if line.startswith('diff'):
             if filename:
                 isbinary = adds == 0 and removes == 0
                 yield (filename, adds, removes, isbinary)
             # set numbers to 0 anyway when starting new file
             adds, removes = 0, 0
             if line.startswith('diff --git'):
                 filename = gitre.search(line).group(1)
             else:
                 # format: "diff -r ... -r ... filename"
                 filename = line.split(None, 5)[-1]
         elif line.startswith('+') and not line.startswith('+++'):
             adds += 1
         elif line.startswith('-') and not line.startswith('---'):
             removes += 1
     if filename:
         isbinary = adds == 0 and removes == 0
         yield (filename, adds, removes, isbinary)
 
 def diffstat(lines, width=80, git=False):
     output = []
     stats = list(diffstatdata(lines))
 
     maxtotal, maxname = 0, 0
     totaladds, totalremoves = 0, 0
     hasbinary = False
     for filename, adds, removes, isbinary in stats:
         totaladds += adds
         totalremoves += removes
         maxname = max(maxname, len(filename))
         maxtotal = max(maxtotal, adds+removes)
         if isbinary:
             hasbinary = True
 
     countwidth = len(str(maxtotal))
     if hasbinary and countwidth < 3:
         countwidth = 3
     graphwidth = width - countwidth - maxname - 6
     if graphwidth < 10:
         graphwidth = 10
 
     def scale(i):
         if maxtotal <= graphwidth:
             return i
         # If diffstat runs out of room it doesn't print anything,
         # which isn't very useful, so always print at least one + or -
         # if there were at least some changes.
         return max(i * graphwidth // maxtotal, int(bool(i)))
 
     for filename, adds, removes, isbinary in stats:
         if git and isbinary:
             count = 'Bin'
         else:
             count = adds + removes
         pluses = '+' * scale(adds)
         minuses = '-' * scale(removes)
         output.append(' %-*s |  %*s %s%s\n' % (maxname, filename, countwidth,
                                                count, pluses, minuses))
 
     if stats:
         output.append(_(' %d files changed, %d insertions(+), %d deletions(-)\n')
                       % (len(stats), totaladds, totalremoves))
 
     return ''.join(output)