[PATCH remotenames] remotenames: use atomictemp when writing files

[Jun Wu]

# HG changeset patch
# User Jun Wu <quark at fb.com>
# Date 1460672160 -3600
#      Thu Apr 14 23:16:00 2016 +0100
# Node ID d3c9e3afef2973f16df7778991cee2ba4990a6bb
# Parent  670f94e39c01fd55663b0e1c7b829f78f54d79ac
remotenames: use atomictemp when writing files

Before this patch, it is possible to have a race condition that a process can
see an incomplete .hg/remotenames and may crash like:

  Traceback (last part):
    File ".../remotenames.py", line 233, in _load
      for node, nametype, remote, rname in readremotenames(repo):
    File ".../remotenames.py", line 1245, in readremotenames
      node, name = line.split(' ', 1)
  ValueError: need more than 1 value to unpack

This patch fixes it and avoids similar issues by using atomictemp for all file
writes.

diff --git a/remotenames.py b/remotenames.py
--- a/remotenames.py
+++ b/remotenames.py
@@ -450,7 +450,7 @@
         if not repo.vfs.isfile('hgrc'):
             raise error.Abort(_("could not find hgrc file"))
         oldhgrc = repo.vfs.read('hgrc').splitlines(True)
-        f = repo.vfs('hgrc', 'w')
+        f = repo.vfs('hgrc', 'w', atomictemp=True)
         for line in oldhgrc:
             if '[paths]' in line:
                 foundpaths = True
@@ -468,7 +468,7 @@
         oldhgrc = []
         if repo.vfs.isfile("hgrc"):
             oldhgrc = repo.vfs.read('hgrc').splitlines(True)
-        f = repo.vfs('hgrc', 'w')
+        f = repo.vfs('hgrc', 'w', atomictemp=True)
         done = False
         for line in oldhgrc:
             if '[paths]' in line:
@@ -1316,7 +1316,7 @@
         olddata = set(readremotenames(repo))
         oldbooks = {}
 
-        f = vfs('remotenames', 'w')
+        f = vfs('remotenames', 'w', atomictemp=True)
 
         # only update the given 'remote path'; iterate over
         # old data and re-save it
@@ -1378,7 +1378,7 @@
 def writedistancecache(repo, distance):
     try:
         vfs = shareawarevfs(repo)
-        f = vfs('cache/distance', 'w')
+        f = vfs('cache/distance', 'w', atomictemp=True)
         for k, v in distance.iteritems():
             f.write('%s %d %d\n' % (k, v[0], v[1]))
     except (IOError, OSError):