Downloadiong and file dates

[Lennart Borgman <lennart.borgman@gmail.com>]

When downloading a file from Launchpad's repository's web interface
the downloaded file does not get the right modified/creation time.

The headers in a buffer downloaded with url-retrieve-synchronously says

HTTP/1.1 200 OK
Date: Mon, 04 Jan 2010 01:50:08 GMT
Server: PasteWSGIServer/0.5 Python/2.5.2
Content-Type: application/octet-stream
Content-Length: 13071
Content-Disposition: attachment; filename*=utf-8''foldit.el
Via: 1.1 bazaar.launchpad.net
Keep-Alive: timeout=15, max=100
Connection: Keep-Alive
Content-Language: el


The "Date" is obviously now when I tested. That seems correct. However
it would be good to have the modification time for the file too. There
is a "Last-Modified" header that perhaps could be used for this. Would
that be correct use for that header?

And how does url-copy-file handle this? This function has an argument
named `keep-time' but it is not easy to see where and how it is used.
From the doc string it looks liike it preserves the date of an old
local file.

Does url-copy-file take care of "Last-Modified" if present? Should it?