hg update: fix clobbering files when going backwards
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hg update: fix clobbering files when going backwards
spotted by Andrew Thompson
manifest hash: 0cfc2d189a395fb8761391d9918864034aa7a9b8
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# lock.py - simple locking scheme for mercurial
#
# Copyright 2005 Matt Mackall <mpm@selenic.com>
#
# This software may be used and distributed according to the terms
# of the GNU General Public License, incorporated herein by reference.
import os, time
class LockHeld(Exception):
pass
class lock:
def __init__(self, file, wait = 1):
self.f = file
self.held = 0
self.wait = wait
self.lock()
def __del__(self):
self.release()
def lock(self):
while 1:
try:
self.trylock()
return 1
except LockHeld, inst:
if self.wait:
time.sleep(1)
continue
raise inst
def trylock(self):
pid = os.getpid()
try:
os.symlink(str(pid), self.f)
self.held = 1
except:
raise LockHeld(os.readlink(self.f))
def release(self):
if self.held:
self.held = 0
os.unlink(self.f)