I think that I can add an option to store and use mtime, instead of
ctime. It won't be on by default, but if someone (actually in most cases
on modern high-time-resolution file systems) trusts his system behaviour,
it could be useful. At least mtime can be kept during copying (cp -a,
tar c | tar x), that is impossible with ctime.

-- 
Sergey Matveev (http://www.stargrave.org/)
OpenPGP: CF60 E89A 5923 1E76 E263  6422 AE1A 8109 E498 57EF