Set file timestamp from mirror source

[keestux]

The create-python-mirror.py script will now set the timestamp of the downloaded files.

Summary

Set the timestamp of the downloaded files as found on the originating server.

Test Plan

Basically run the mirror script and afterwards check the timestamp of newly
downloaded files. The timestamps will be different from the current time.
Files that were already present (with correct checksum) will not be changed.

[konstin]

Why do we need the file timestamp for it if we already have the SHA check?

[keestux]

Why do we need the file timestamp for it if we already have the SHA check?

It's a convenience. I'm copying the downloaded files to some other location with rsync -ia ..., the output will be more informative if unchanged files are skipped. Also, if I want to clean up old files I need useful timestamps.

[konstin]

I wouldn't manually backdate the timestamps of files, since it can break e.g. the rsync workflow you mentioned, where rsync would then skip those files even though they were actually updated. Since the file doesn't change after the first download, rsync shouldn't re-copy it.

Regarding cleaning up files, it seems that the timestamp is the wrong measure for this (especially backdated ones), and should rather be based on what files the deployment needs.