nixUnstable is a deprecated alias, so the script didn't work anymore.
Also, I see no need to avoid the default nix here (maybe years ago).
Tested on mirror-tarballs.service at pluto.nixos.org (atop 24.05).
(cherry picked from commit bf8e7f9cb3)
When DEBUG is defined, the script just prints the URL's without actually
checking whether they're already cached or downloading/uploading anything.
That got broken because connecting to S3 now fails fast. This PR makes sure
we skip connecting to s3 in DEBUG mode.
This should fix
Jul 20 07:16:12 bastion mirror-tarballs-start[21663]: Use of uninitialized value $algo in concatenation (.) or string at ./maintainers/scripts/copy-tarballs.pl line 80.
Jul 20 07:16:12 bastion mirror-tarballs-start[21663]: Use of uninitialized value in subroutine entry at ./maintainers/scripts/copy-tarballs.pl line 185.
Jul 20 07:16:13 bastion mirror-tarballs-start[21663]: error: unknown hash algorithm '' at ./maintainers/scripts/copy-tarballs.pl line 185.
Tarballs.nixos.org is now stored in an S3 bucket rather than an EBS
volume. Redirects are used to simulate symlinks.
The function find-tarballs.nix now filters out fetchzip, fetchpatch
and the like.
