Mercurial > hg
view mercurial/lock.py @ 16696:d1afbf03e69a
rebase: allow collapsing branches in place (issue3111)
We allow rebase plus collapse, but not collapse only? I imagine people would
rebase first then collapse once they are sure the rebase is correct and it is
the right time to finish it.
I was reluctant to submit this patch for reasons detailed below, but it
improves rebase --collapse usefulness so much it is worth the ugliness.
The fix is ugly because we should be fixing the collapse code path rather than
the merge. Collapsing by merging changesets repeatedly is inefficient compared
to what commit --amend does: commitctx(), update, strip. The problem with the
latter is, to generate the synthetic changeset, copy records are gathered with
copies.pathcopies(). copies.pathcopies() is still implemented with merging in
mind and discards information like file replaced by the copy of another,
criss-cross copies and so forth. I believe this information should not be lost,
even if we decide not to interpret it fully later, at merge time.
The second issue with improving rebase --collapse is the option should not be
there to begin with. Rebasing and collapsing are orthogonal and a dedicated
command would probably enable a better, simpler ui. We should avoid advertizing
rebase --collapse, but with this fix it becomes the best shipped solution to
collapse changesets.
And for the record, available techniques are:
- revert + commit + strip: lose copies
- mq/qfold: repeated patching() (mostly correct, fragile)
- rebase: repeated merges (mostly correct, fragile)
- collapse: revert + tag rewriting wizardry, lose copies
- histedit: repeated patching() (mostly correct, fragile)
- amend: copies.pathcopies() + commitctx() + update + strip
author | Patrick Mezard <patrick@mezard.eu> |
---|---|
date | Thu, 03 May 2012 15:14:58 +0200 |
parents | cc24e4ed3e0c |
children | e7cfe3587ea4 7c44b703657b 829919ef894a |
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# lock.py - simple advisory locking scheme for mercurial # # 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. import util, error import errno, os, socket, time import warnings class lock(object): '''An advisory lock held by one process to control access to a set of files. Non-cooperating processes or incorrectly written scripts can ignore Mercurial's locking scheme and stomp all over the repository, so don't do that. Typically used via localrepository.lock() to lock the repository store (.hg/store/) or localrepository.wlock() to lock everything else under .hg/.''' # lock is symlink on platforms that support it, file on others. # symlink is used because create of directory entry and contents # are atomic even over nfs. # old-style lock: symlink to pid # new-style lock: symlink to hostname:pid _host = None def __init__(self, file, timeout=-1, releasefn=None, desc=None): self.f = file self.held = 0 self.timeout = timeout self.releasefn = releasefn self.desc = desc self.postrelease = [] self.lock() def __del__(self): if self.held: warnings.warn("use lock.release instead of del lock", category=DeprecationWarning, stacklevel=2) # ensure the lock will be removed # even if recursive locking did occur self.held = 1 self.release() def lock(self): timeout = self.timeout while True: try: self.trylock() return 1 except error.LockHeld, inst: if timeout != 0: time.sleep(1) if timeout > 0: timeout -= 1 continue raise error.LockHeld(errno.ETIMEDOUT, inst.filename, self.desc, inst.locker) def trylock(self): if self.held: self.held += 1 return if lock._host is None: lock._host = socket.gethostname() lockname = '%s:%s' % (lock._host, os.getpid()) while not self.held: try: util.makelock(lockname, self.f) self.held = 1 except (OSError, IOError), why: if why.errno == errno.EEXIST: locker = self.testlock() if locker is not None: raise error.LockHeld(errno.EAGAIN, self.f, self.desc, locker) else: raise error.LockUnavailable(why.errno, why.strerror, why.filename, self.desc) def testlock(self): """return id of locker if lock is valid, else None. If old-style lock, we cannot tell what machine locker is on. with new-style lock, if locker is on this machine, we can see if locker is alive. If locker is on this machine but not alive, we can safely break lock. The lock file is only deleted when None is returned. """ locker = util.readlock(self.f) try: host, pid = locker.split(":", 1) except ValueError: return locker if host != lock._host: return locker try: pid = int(pid) except ValueError: return locker if util.testpid(pid): return locker # if locker dead, break lock. must do this with another lock # held, or can race and break valid lock. try: l = lock(self.f + '.break', timeout=0) util.unlink(self.f) l.release() except error.LockError: return locker def release(self): """release the lock and execute callback function if any If the lock have been aquired multiple time, the actual release is delayed to the last relase call.""" if self.held > 1: self.held -= 1 elif self.held == 1: self.held = 0 if self.releasefn: self.releasefn() try: util.unlink(self.f) except OSError: pass for callback in self.postrelease: callback() def release(*locks): for lock in locks: if lock is not None: lock.release()