view mercurial/diffhelper.py @ 39366:a41497b5117c

copies: improve logic of deciding copytracing on based of config options

Few months ago or maybe a year ago, I imported Fb's heuristics based copytracing
algorithms. While importing that, I renamed `experimental.disablecopytrace` with
`experimental.copytrace` and the behavior of the new config option was like
this:

  * "heuristics" : Fb's heuristic copytracing algorithm
  * "off" : copytracing is turned off
  * something else: copytracing is on

This is the behavior right now also and this is bad because it hardcodes the
string 'off' to turn off the copytracing. On big repositories, copytracing is
very slow and people wants to turn copytracing off. However if the user sets it
to 'False', 'Off', '0', none of them is going to disbale copytracing while they
should.
I lacked the understanding of why this can be bad when I coded it.

After this patch, the new behavior of the config option will be:

  * "heuristics": Fb's heuristic copytracing algorithm
  * '0', 'false', 'off', 'never', 'no', 'NO', all the values which
    repo.ui.configbool() evaluates to False: copytracing in turned off
  * something else: copytracing is on

Since 'off' still evaluates to copytracing being turned off, this is not BC.
Also the config option is experimental.

Differential Revision: https://phab.mercurial-scm.org/D4416

# diffhelper.py - helper routines for patch
#
# 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

from .i18n import _

from . import (
    error,
    pycompat,
)

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 pycompat.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 pycompat.xrange(alen):
        if a[i][1:] != b[i + bstart]:
            return False
    return True