similar: compare between actual file contents for exact identity
Before this patch, similarity detection logic (for addremove and
automv) depends entirely on SHA-1 digesting. But this causes incorrect
rename detection, if:
- removing file A and adding file B occur at same committing, and
- SHA-1 hash values of file A and B are same
This may prevent security experts from managing sample files for
SHAttered issue in Mercurial repository, for example.
https://security.googleblog.com/2017/02/announcing-first-sha1-collision.html
https://shattered.it/
Hash collision itself isn't so serious for core repository
functionality of Mercurial, described by mpm as below, though.
https://www.mercurial-scm.org/wiki/mpm/SHA1
This patch compares between actual file contents after hash comparison
for exact identity.
Even after this patch, SHA-1 is still used, because it is reasonable
enough to quickly detect existence of "(almost) same" file.
- replacing SHA-1 causes decreasing performance, and
- replacement of it has ambiguity, yet
Getting content of removed file (= rfctx.data()) at each exact
comparison should be cheap enough, even though getting content of
added one costs much.
======= ============== =====================
file fctx data() reads from
======= ============== =====================
removed filectx in-memory revlog data
added workingfilectx storage
======= ============== =====================
# Copyright (C) 2004, 2005 Canonical Ltd
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, see <http://www.gnu.org/licenses/>.
# mbp: "you know that thing where cvs gives you conflict markers?"
# s: "i hate that."
from __future__ import absolute_import
import os
from .i18n import _
from . import (
error,
mdiff,
scmutil,
util,
)
class CantReprocessAndShowBase(Exception):
pass
def intersect(ra, rb):
"""Given two ranges return the range where they intersect or None.
>>> intersect((0, 10), (0, 6))
(0, 6)
>>> intersect((0, 10), (5, 15))
(5, 10)
>>> intersect((0, 10), (10, 15))
>>> intersect((0, 9), (10, 15))
>>> intersect((0, 9), (7, 15))
(7, 9)
"""
assert ra[0] <= ra[1]
assert rb[0] <= rb[1]
sa = max(ra[0], rb[0])
sb = min(ra[1], rb[1])
if sa < sb:
return sa, sb
else:
return None
def compare_range(a, astart, aend, b, bstart, bend):
"""Compare a[astart:aend] == b[bstart:bend], without slicing.
"""
if (aend - astart) != (bend - bstart):
return False
for ia, ib in zip(xrange(astart, aend), xrange(bstart, bend)):
if a[ia] != b[ib]:
return False
else:
return True
class Merge3Text(object):
"""3-way merge of texts.
Given strings BASE, OTHER, THIS, tries to produce a combined text
incorporating the changes from both BASE->OTHER and BASE->THIS."""
def __init__(self, basetext, atext, btext, base=None, a=None, b=None):
self.basetext = basetext
self.atext = atext
self.btext = btext
if base is None:
base = mdiff.splitnewlines(basetext)
if a is None:
a = mdiff.splitnewlines(atext)
if b is None:
b = mdiff.splitnewlines(btext)
self.base = base
self.a = a
self.b = b
def merge_lines(self,
name_a=None,
name_b=None,
name_base=None,
start_marker='<<<<<<<',
mid_marker='=======',
end_marker='>>>>>>>',
base_marker=None,
localorother=None,
minimize=False):
"""Return merge in cvs-like form.
"""
self.conflicts = False
newline = '\n'
if len(self.a) > 0:
if self.a[0].endswith('\r\n'):
newline = '\r\n'
elif self.a[0].endswith('\r'):
newline = '\r'
if name_a and start_marker:
start_marker = start_marker + ' ' + name_a
if name_b and end_marker:
end_marker = end_marker + ' ' + name_b
if name_base and base_marker:
base_marker = base_marker + ' ' + name_base
merge_regions = self.merge_regions()
if minimize:
merge_regions = self.minimize(merge_regions)
for t in merge_regions:
what = t[0]
if what == 'unchanged':
for i in range(t[1], t[2]):
yield self.base[i]
elif what == 'a' or what == 'same':
for i in range(t[1], t[2]):
yield self.a[i]
elif what == 'b':
for i in range(t[1], t[2]):
yield self.b[i]
elif what == 'conflict':
if localorother == 'local':
for i in range(t[3], t[4]):
yield self.a[i]
elif localorother == 'other':
for i in range(t[5], t[6]):
yield self.b[i]
else:
self.conflicts = True
if start_marker is not None:
yield start_marker + newline
for i in range(t[3], t[4]):
yield self.a[i]
if base_marker is not None:
yield base_marker + newline
for i in range(t[1], t[2]):
yield self.base[i]
if mid_marker is not None:
yield mid_marker + newline
for i in range(t[5], t[6]):
yield self.b[i]
if end_marker is not None:
yield end_marker + newline
else:
raise ValueError(what)
def merge_groups(self):
"""Yield sequence of line groups. Each one is a tuple:
'unchanged', lines
Lines unchanged from base
'a', lines
Lines taken from a
'same', lines
Lines taken from a (and equal to b)
'b', lines
Lines taken from b
'conflict', base_lines, a_lines, b_lines
Lines from base were changed to either a or b and conflict.
"""
for t in self.merge_regions():
what = t[0]
if what == 'unchanged':
yield what, self.base[t[1]:t[2]]
elif what == 'a' or what == 'same':
yield what, self.a[t[1]:t[2]]
elif what == 'b':
yield what, self.b[t[1]:t[2]]
elif what == 'conflict':
yield (what,
self.base[t[1]:t[2]],
self.a[t[3]:t[4]],
self.b[t[5]:t[6]])
else:
raise ValueError(what)
def merge_regions(self):
"""Return sequences of matching and conflicting regions.
This returns tuples, where the first value says what kind we
have:
'unchanged', start, end
Take a region of base[start:end]
'same', astart, aend
b and a are different from base but give the same result
'a', start, end
Non-clashing insertion from a[start:end]
'conflict', zstart, zend, astart, aend, bstart, bend
Conflict between a and b, with z as common ancestor
Method is as follows:
The two sequences align only on regions which match the base
and both descendants. These are found by doing a two-way diff
of each one against the base, and then finding the
intersections between those regions. These "sync regions"
are by definition unchanged in both and easily dealt with.
The regions in between can be in any of three cases:
conflicted, or changed on only one side.
"""
# section a[0:ia] has been disposed of, etc
iz = ia = ib = 0
for region in self.find_sync_regions():
zmatch, zend, amatch, aend, bmatch, bend = region
#print 'match base [%d:%d]' % (zmatch, zend)
matchlen = zend - zmatch
assert matchlen >= 0
assert matchlen == (aend - amatch)
assert matchlen == (bend - bmatch)
len_a = amatch - ia
len_b = bmatch - ib
len_base = zmatch - iz
assert len_a >= 0
assert len_b >= 0
assert len_base >= 0
#print 'unmatched a=%d, b=%d' % (len_a, len_b)
if len_a or len_b:
# try to avoid actually slicing the lists
equal_a = compare_range(self.a, ia, amatch,
self.base, iz, zmatch)
equal_b = compare_range(self.b, ib, bmatch,
self.base, iz, zmatch)
same = compare_range(self.a, ia, amatch,
self.b, ib, bmatch)
if same:
yield 'same', ia, amatch
elif equal_a and not equal_b:
yield 'b', ib, bmatch
elif equal_b and not equal_a:
yield 'a', ia, amatch
elif not equal_a and not equal_b:
yield 'conflict', iz, zmatch, ia, amatch, ib, bmatch
else:
raise AssertionError("can't handle a=b=base but unmatched")
ia = amatch
ib = bmatch
iz = zmatch
# if the same part of the base was deleted on both sides
# that's OK, we can just skip it.
if matchlen > 0:
assert ia == amatch
assert ib == bmatch
assert iz == zmatch
yield 'unchanged', zmatch, zend
iz = zend
ia = aend
ib = bend
def minimize(self, merge_regions):
"""Trim conflict regions of lines where A and B sides match.
Lines where both A and B have made the same changes at the beginning
or the end of each merge region are eliminated from the conflict
region and are instead considered the same.
"""
for region in merge_regions:
if region[0] != "conflict":
yield region
continue
issue, z1, z2, a1, a2, b1, b2 = region
alen = a2 - a1
blen = b2 - b1
# find matches at the front
ii = 0
while ii < alen and ii < blen and \
self.a[a1 + ii] == self.b[b1 + ii]:
ii += 1
startmatches = ii
# find matches at the end
ii = 0
while ii < alen and ii < blen and \
self.a[a2 - ii - 1] == self.b[b2 - ii - 1]:
ii += 1
endmatches = ii
if startmatches > 0:
yield 'same', a1, a1 + startmatches
yield ('conflict', z1, z2,
a1 + startmatches, a2 - endmatches,
b1 + startmatches, b2 - endmatches)
if endmatches > 0:
yield 'same', a2 - endmatches, a2
def find_sync_regions(self):
"""Return a list of sync regions, where both descendants match the base.
Generates a list of (base1, base2, a1, a2, b1, b2). There is
always a zero-length sync region at the end of all the files.
"""
ia = ib = 0
amatches = mdiff.get_matching_blocks(self.basetext, self.atext)
bmatches = mdiff.get_matching_blocks(self.basetext, self.btext)
len_a = len(amatches)
len_b = len(bmatches)
sl = []
while ia < len_a and ib < len_b:
abase, amatch, alen = amatches[ia]
bbase, bmatch, blen = bmatches[ib]
# there is an unconflicted block at i; how long does it
# extend? until whichever one ends earlier.
i = intersect((abase, abase + alen), (bbase, bbase + blen))
if i:
intbase = i[0]
intend = i[1]
intlen = intend - intbase
# found a match of base[i[0], i[1]]; this may be less than
# the region that matches in either one
assert intlen <= alen
assert intlen <= blen
assert abase <= intbase
assert bbase <= intbase
asub = amatch + (intbase - abase)
bsub = bmatch + (intbase - bbase)
aend = asub + intlen
bend = bsub + intlen
assert self.base[intbase:intend] == self.a[asub:aend], \
(self.base[intbase:intend], self.a[asub:aend])
assert self.base[intbase:intend] == self.b[bsub:bend]
sl.append((intbase, intend,
asub, aend,
bsub, bend))
# advance whichever one ends first in the base text
if (abase + alen) < (bbase + blen):
ia += 1
else:
ib += 1
intbase = len(self.base)
abase = len(self.a)
bbase = len(self.b)
sl.append((intbase, intbase, abase, abase, bbase, bbase))
return sl
def find_unconflicted(self):
"""Return a list of ranges in base that are not conflicted."""
am = mdiff.get_matching_blocks(self.basetext, self.atext)
bm = mdiff.get_matching_blocks(self.basetext, self.btext)
unc = []
while am and bm:
# there is an unconflicted block at i; how long does it
# extend? until whichever one ends earlier.
a1 = am[0][0]
a2 = a1 + am[0][2]
b1 = bm[0][0]
b2 = b1 + bm[0][2]
i = intersect((a1, a2), (b1, b2))
if i:
unc.append(i)
if a2 < b2:
del am[0]
else:
del bm[0]
return unc
def simplemerge(ui, local, base, other, **opts):
def readfile(filename):
f = open(filename, "rb")
text = f.read()
f.close()
if util.binary(text):
msg = _("%s looks like a binary file.") % filename
if not opts.get('quiet'):
ui.warn(_('warning: %s\n') % msg)
if not opts.get('text'):
raise error.Abort(msg)
return text
mode = opts.get('mode','merge')
if mode == 'union':
name_a = None
name_b = None
name_base = None
else:
name_a = local
name_b = other
name_base = None
labels = opts.get('label', [])
if len(labels) > 0:
name_a = labels[0]
if len(labels) > 1:
name_b = labels[1]
if len(labels) > 2:
name_base = labels[2]
if len(labels) > 3:
raise error.Abort(_("can only specify three labels."))
try:
localtext = readfile(local)
basetext = readfile(base)
othertext = readfile(other)
except error.Abort:
return 1
local = os.path.realpath(local)
if not opts.get('print'):
opener = scmutil.opener(os.path.dirname(local))
out = opener(os.path.basename(local), "w", atomictemp=True)
else:
out = ui.fout
m3 = Merge3Text(basetext, localtext, othertext)
extrakwargs = {
"localorother": opts.get("localorother", None),
'minimize': True,
}
if mode == 'union':
extrakwargs['start_marker'] = None
extrakwargs['mid_marker'] = None
extrakwargs['end_marker'] = None
elif name_base is not None:
extrakwargs['base_marker'] = '|||||||'
extrakwargs['name_base'] = name_base
extrakwargs['minimize'] = False
for line in m3.merge_lines(name_a=name_a, name_b=name_b, **extrakwargs):
out.write(line)
if not opts.get('print'):
out.close()
if m3.conflicts and not mode == 'union':
return 1