File dates displayed in destinations

When displaying the dates of files saved in destinations, backup_migrate currently uses the ctime of the file. I would like to argue that the mtime is more useful. Attached is a very simple one-line patch to change the use of filectime() to filemtime().

ctime (last change) is basically immutable on unix-like systems and is set by the file system. One is normally only allowed to modify atime (last access) and mtime (last modified).

When using a revision control system while staging your site on a development server, the files copied down from elsewhere are all going to have identical ctime's. This is because they are all created more or less simultaneously by the RCS. Any attempts by the RCS or the user to "correct" the file times by changing mtime or atime are not seen by backup_migrate because it is watching ctime. The upshot is that when one uses descriptive names in the manual backup destination, there is no way to tell the order in which the backups were originally created.

I can't imagine that this is a common difficulty; but I think mtime is more useful. ctime will also change if the name of the file is changed; while mtime should more accurately continue to reflect the time when the file was originally created.

ctime is also used in files.inc to determine whether a file has aged out and should be deleted; but I left that one alone since it's arguable that if someone even sniffs at a file that the expiration clock should reset (it's arguable the other way too...)

Thanks for your time.