[PATCH 2 of 3 STABLE] vfs: ignore EPERM at os.utime, which avoids ambiguity at renaming (issue5418)

[FUJIWARA Katsunori]

# HG changeset patch
# User FUJIWARA Katsunori <foozy at lares.dti.ne.jp>
# Date 1478985116 -32400
#      Sun Nov 13 06:11:56 2016 +0900
# Branch stable
# Node ID bff5ccbe5ead56aac7fff30f48a486007d469f3f
# Parent  b496a464399cb68628b09e52aa8cf379c98428e6
vfs: ignore EPERM at os.utime, which avoids ambiguity at renaming (issue5418)

According to POSIX specification, just having group write access to a
file causes EPERM at invocation of os.utime() with an explicit time
information (e.g. working on the repository shared by group access
permission).

To ignore EPERM at renaming in such case, this patch makes
vfs.rename() use filestat.avoidambig() introduced by previous patch.

diff --git a/mercurial/scmutil.py b/mercurial/scmutil.py
--- a/mercurial/scmutil.py
+++ b/mercurial/scmutil.py
@@ -390,8 +390,7 @@ class abstractvfs(object):
             newstat = util.filestat(dstpath)
             if newstat.isambig(oldstat):
                 # stat of renamed file is ambiguous to original one
-                advanced = (oldstat.stat.st_mtime + 1) & 0x7fffffff
-                os.utime(dstpath, (advanced, advanced))
+                newstat.avoidambig(dstpath, oldstat)
             return ret
         return util.rename(self.join(src), dstpath)