merge: fast-forward merge with descendant
issue2538 gives a case where a changeset is merged with its child (which is on
another branch), and to my surprise the result is a real merge with two
parents, not just a "fast forward" "merge" with only the child as parent.
That is essentially the same as issue619.
Is the existing behaviour as intended and correct?
Or is the following fix correct?
Some extra "created new head" pops up with this fix, but it seems to me like
they could be considered correct. The old branch head has been superseeded by
changes on the other branch, and when the changes on the other branch is merged
back to the branch it will introduce a new head not directly related to the
previous branch head.
(I guess the intention with existing behaviour could be to ensure that the
changesets on the branch are directly connected and that no new heads pops up
on merges.)
# transaction.py - simple journalling scheme for mercurial
#
# This transaction scheme is intended to gracefully handle program
# errors and interruptions. More serious failures like system crashes
# can be recovered with an fsck-like tool. As the whole repository is
# effectively log-structured, this should amount to simply truncating
# anything that isn't referenced in the changelog.
#
# Copyright 2005, 2006 Matt Mackall <mpm@selenic.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from i18n import _
import os, errno
import error
def active(func):
def _active(self, *args, **kwds):
if self.count == 0:
raise error.Abort(_(
'cannot use transaction when it is already committed/aborted'))
return func(self, *args, **kwds)
return _active
def _playback(journal, report, opener, entries, unlink=True):
for f, o, ignore in entries:
if o or not unlink:
try:
opener(f, 'a').truncate(o)
except IOError:
report(_("failed to truncate %s\n") % f)
raise
else:
try:
fn = opener(f).name
os.unlink(fn)
except (IOError, OSError), inst:
if inst.errno != errno.ENOENT:
raise
os.unlink(journal)
class transaction(object):
def __init__(self, report, opener, journal, after=None, createmode=None):
self.count = 1
self.usages = 1
self.report = report
self.opener = opener
self.after = after
self.entries = []
self.map = {}
self.journal = journal
self._queue = []
self.file = open(self.journal, "w")
if createmode is not None:
os.chmod(self.journal, createmode & 0666)
def __del__(self):
if self.journal:
self._abort()
@active
def startgroup(self):
self._queue.append([])
@active
def endgroup(self):
q = self._queue.pop()
d = ''.join(['%s\0%d\n' % (x[0], x[1]) for x in q])
self.entries.extend(q)
self.file.write(d)
self.file.flush()
@active
def add(self, file, offset, data=None):
if file in self.map:
return
if self._queue:
self._queue[-1].append((file, offset, data))
return
self.entries.append((file, offset, data))
self.map[file] = len(self.entries) - 1
# add enough data to the journal to do the truncate
self.file.write("%s\0%d\n" % (file, offset))
self.file.flush()
@active
def find(self, file):
if file in self.map:
return self.entries[self.map[file]]
return None
@active
def replace(self, file, offset, data=None):
'''
replace can only replace already committed entries
that are not pending in the queue
'''
if file not in self.map:
raise KeyError(file)
index = self.map[file]
self.entries[index] = (file, offset, data)
self.file.write("%s\0%d\n" % (file, offset))
self.file.flush()
@active
def nest(self):
self.count += 1
self.usages += 1
return self
def release(self):
if self.count > 0:
self.usages -= 1
# if the transaction scopes are left without being closed, fail
if self.count > 0 and self.usages == 0:
self._abort()
def running(self):
return self.count > 0
@active
def close(self):
'''commit the transaction'''
self.count -= 1
if self.count != 0:
return
self.file.close()
self.entries = []
if self.after:
self.after()
if os.path.isfile(self.journal):
os.unlink(self.journal)
self.journal = None
@active
def abort(self):
'''abort the transaction (generally called on error, or when the
transaction is not explicitly committed before going out of
scope)'''
self._abort()
def _abort(self):
self.count = 0
self.usages = 0
self.file.close()
try:
if not self.entries:
if self.journal:
os.unlink(self.journal)
return
self.report(_("transaction abort!\n"))
try:
_playback(self.journal, self.report, self.opener,
self.entries, False)
self.report(_("rollback completed\n"))
except:
self.report(_("rollback failed - please run hg recover\n"))
finally:
self.journal = None
def rollback(opener, file, report):
entries = []
for l in open(file).readlines():
f, o = l.split('\0')
entries.append((f, int(o), None))
_playback(file, report, opener, entries)