changelog: specify checkambig=True to revlog.__init__, to avoid ambiguity
If steps below occurs at "the same time in sec", all of mtime, ctime
and size are same between (1) and (3).
1. append data to 00changelog.i (and close transaction)
2. discard appended data by truncation (strip or rollback)
3. append same size but different data to 00changelog.i again
Therefore, cache validation doesn't work after (3) as expected.
To avoid such file stat ambiguity around truncation, this patch
specifies checkambig=True to revlog.__init__(). This makes revlog
write changes out with checkambig=True.
Even though changes of 00changelog.i themselves are written out at
changelog._finalize(), this checkambig=True is needed, because
revlog.checkinlinesize(), which is invoked at the end of
changelog._finalize(), might replace already changed 00changelog.i by
converted one.
Even after this patch, avoiding file stat ambiguity of 00changelog.i
around truncation isn't yet completed, because truncation side isn't
aware of this issue.
This is a part of ExactCacheValidationPlan.
https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan
# diffhelpers.py - pure Python implementation of diffhelpers.c
#
# Copyright 2009 Matt Mackall <mpm@selenic.com> 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
def addlines(fp, hunk, lena, lenb, a, b):
while True:
todoa = lena - len(a)
todob = lenb - len(b)
num = max(todoa, todob)
if num == 0:
break
for i in xrange(num):
s = fp.readline()
c = s[0]
if s == "\\ No newline at end of file\n":
fix_newline(hunk, a, b)
continue
if c == "\n":
# Some patches may be missing the control char
# on empty lines. Supply a leading space.
s = " \n"
hunk.append(s)
if c == "+":
b.append(s[1:])
elif c == "-":
a.append(s)
else:
b.append(s[1:])
a.append(s)
return 0
def fix_newline(hunk, a, b):
l = hunk[-1]
# tolerate CRLF in last line
if l.endswith('\r\n'):
hline = l[:-2]
else:
hline = l[:-1]
c = hline[0]
if c in " +":
b[-1] = hline[1:]
if c in " -":
a[-1] = hline
hunk[-1] = hline
return 0
def testhunk(a, b, bstart):
alen = len(a)
blen = len(b)
if alen > blen - bstart:
return -1
for i in xrange(alen):
if a[i][1:] != b[i + bstart]:
return -1
return 0