In reading through update.c, it doesn't look as though updates or reverts will set the permissions of files when recreating them.  Unlike checkout's code path, update/revert doesn't call checkout.c:checkout_set_all_exe() to set the permissions of files.  At first glance, it looks like the best place to check to see if permissions need to be updated is via vfile.c:vfile_check_signature() (in the call path for revert) or in vfile.c:vfile_compare_repository_to_disk() (not used other than in checkin).

To reproduce:

<pre># In a test repository with `alias fs fossil`
printf '#\!/bin/sh\necho test script perms\n' > test.sh
chmod 755 test.sh
fs add test.sh
fs ci -m "Adding a test script"
rm -f test.sh
fs revert test.sh
# test.sh will be mode 644</pre>