view mercurial/diffhelper.py @ 39494:e72130f58f5d

snapshot: consider all snapshots in the parents' chains

There are no reasons to only consider full snapshot as a possible base for an
intermediate snapshot.  Now that the basic principles have been set, we can
start adding more levels of snapshots.

We now consider all snapshots in the parent's chains (full or intermediate).
This creates a chain of intermediate snapshots, each smaller than the previous
one.

# Effect On The Test Repository

In the test repository, we can see a decrease in the revlog size and slightly
shorter delta chain.

However, that approach creates snapshots more frequently, increasing the risk
of ending into problematic cases in very branchy repositories (not triggered
by the test repository). The next changesets will remove that risk by adding
logic that increases deltas reuse.

# 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