rsync isn't resilient about updating symbolic link times

rsync isn't resilient about updating symbolic link times, so catch a case that
might cause trouble and work around it.

BUG=26181
TEST=keystone_install_test.sh
It should now be possible to update Chrome when you have write permission on
all of the directories but none of the files or symbolic links on disk.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=30768

[TVL, 2009-11-02 23:13:13]

is it worth creating a bunch of DMGs/tars/something that the test can create on
disk and make sure "the right thing happen" even if you have to run the test
manually (because of sudo for setup)?

http://codereview.chromium.org/341072/diff/1/2
File chrome/tools/build/mac/keystone_install.sh (right):

http://codereview.chromium.org/341072/diff/1/2#newcode37
Line 37: if [ -z "${LINKUSER}" ] || [ -z "${LINKGROUP}" ] ; then
how would these be empty strings?

http://codereview.chromium.org/341072/diff/1/2#newcode98
Line 98: return 0
zero?  if you failed to read where the link points to, return true?

http://codereview.chromium.org/341072/diff/1/2#newcode201
Line 201: # Reset ${IFS} to deal properly with spaces in the for loop.
"properly" == "don't use spaces as a break in the for loop?"

[Mark Mentovai, 2009-11-02 23:18:11]

"break on spaces" comment updated

http://codereview.chromium.org/341072/diff/1/2
File chrome/tools/build/mac/keystone_install.sh (right):

http://codereview.chromium.org/341072/diff/1/2#newcode1
Line 1: #!/bin/bash
dmg/tar/whatever: kind of "not really" because you'll still need to be root to
get ownership on/transferred/whatever.

http://codereview.chromium.org/341072/diff/1/2#newcode37
Line 37: if [ -z "${LINKUSER}" ] || [ -z "${LINKGROUP}" ] ; then
TVL wrote:
> how would these be empty strings? 

Shouldn't happen if LINKMODE wasn't empty, but it's possible to maybe run into a
"no more space for you in the process table" condition.

http://codereview.chromium.org/341072/diff/1/2#newcode98
Line 98: return 0
TVL wrote:
> zero?  if you failed to read where the link points to, return true?

This function always returns true, it doesn't really matter what happens.  Think
of it as a void function.  I always use 0 because sh functions always have
return types - if you leave the return value off, it just uses ${?}, the last
exit status.

[TVL, 2009-11-02 23:25:21]

lgtm