view mercurial/pure/bdiff.py @ 45465:9bd60ec60601

tests: add criss cross merging tests whose behavior need to be fixed

Merging two changesets can mark a file as removed post merge. However, in some
cases, a user might not want to remove that file and they revert the removal
back and commit the merge. All this works perfectly well.

However, when we do criss-cross merges with such merge where user explicitly
choose to revert the removal with one where another user choose the removal,
we does not get any conflict.

The intent here is conflicting and merge should result in conflicts. One user
merged and want to keep the file while other user merged and want to remove the
file. Merging those merges should result in conflicts.

This patch adds test cases for these cases.

Differential Revision: https://phab.mercurial-scm.org/D8939

# bdiff.py - Python implementation of bdiff.c
#
# Copyright 2009 Matt Mackall <[e-mail]> 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

import difflib
import re
import struct


def splitnewlines(text):
    '''like str.splitlines, but only split on newlines.'''
    lines = [l + b'\n' for l in text.split(b'\n')]
    if lines:
        if lines[-1] == b'\n':
            lines.pop()
        else:
            lines[-1] = lines[-1][:-1]
    return lines


def _normalizeblocks(a, b, blocks):
    prev = None
    r = []
    for curr in blocks:
        if prev is None:
            prev = curr
            continue
        shift = 0

        a1, b1, l1 = prev
        a1end = a1 + l1
        b1end = b1 + l1

        a2, b2, l2 = curr
        a2end = a2 + l2
        b2end = b2 + l2
        if a1end == a2:
            while (
                a1end + shift < a2end and a[a1end + shift] == b[b1end + shift]
            ):
                shift += 1
        elif b1end == b2:
            while (
                b1end + shift < b2end and a[a1end + shift] == b[b1end + shift]
            ):
                shift += 1
        r.append((a1, b1, l1 + shift))
        prev = a2 + shift, b2 + shift, l2 - shift
    r.append(prev)
    return r


def bdiff(a, b):
    a = bytes(a).splitlines(True)
    b = bytes(b).splitlines(True)

    if not a:
        s = b"".join(b)
        return s and (struct.pack(b">lll", 0, 0, len(s)) + s)

    bin = []
    p = [0]
    for i in a:
        p.append(p[-1] + len(i))

    d = difflib.SequenceMatcher(None, a, b).get_matching_blocks()
    d = _normalizeblocks(a, b, d)
    la = 0
    lb = 0
    for am, bm, size in d:
        s = b"".join(b[lb:bm])
        if am > la or s:
            bin.append(struct.pack(b">lll", p[la], p[am], len(s)) + s)
        la = am + size
        lb = bm + size

    return b"".join(bin)


def blocks(a, b):
    an = splitnewlines(a)
    bn = splitnewlines(b)
    d = difflib.SequenceMatcher(None, an, bn).get_matching_blocks()
    d = _normalizeblocks(an, bn, d)
    return [(i, i + n, j, j + n) for (i, j, n) in d]


def fixws(text, allws):
    if allws:
        text = re.sub(b'[ \t\r]+', b'', text)
    else:
        text = re.sub(b'[ \t\r]+', b' ', text)
        text = text.replace(b' \n', b'\n')
    return text