dev/releases: Document automatic mirroring of releases

[fingolfin]

The last two manual steps of a release — copying the archives to
https://files.gap-system.org and building the manuals for
https://docs.gap-system.org — were done over SSH and were easy to forget. Both
hosts now poll GitHub hourly and pick up any release they do not have yet, so
neither needs a step in this guide any more.

This drops those steps from both the quick and the detailed guide, and instead
documents how to check on the two jobs, how to trigger them early, and the fact
that both deliberately ignore pre-releases: nothing appears until the release has
been switched from "pre-release" to "latest release". The scripts that used to do
this by hand, download_release.sh and download_manuals.sh, remain on the
respective hosts as a fallback and are mentioned as such.

The automation lives in:

• https://github.com/gap-system/gap-files for the release archives — deployed
  and running.
• etc/mirror-manuals.py in gap-system/GapWWW for the manuals — see
  Automate updating the manuals on docs.gap-system.org GapWWW#416.

Important

Please do not merge this before gap-system/GapWWW#416 is merged and its
timer has been enabled on the docs host. The files.gap-system.org half is
already live, but until then this would describe manual building as automatic.

AI disclosure: prepared with Claude Code, which drafted this change and this
description; reviewed by the pull request author.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 79.04%. Comparing base (8215f5d) to head (62789df).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6476      +/-   ##
==========================================
- Coverage   79.04%   79.04%   -0.01%     
==========================================
  Files         685      685              
  Lines      293710   293710              
  Branches     8664     8664              
==========================================
- Hits       232169   232167       -2     
- Misses      59740    59743       +3     
+ Partials     1801     1800       -1     

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[fingolfin]

The dependency is satisfied: gap-system/GapWWW#416 is merged, and the timer is now enabled and verified on the docs host — a run through systemd reports Result=success and correctly finds nothing to build, since all 10 installed releases are up to date. Both hosts are therefore live, so this is ready to merge.

[ruthhoffmann]

Looks good to me! Glad to see that the last manual steps are now gone too.

Can’t spot any typos.

[ThomasBreuer]

Looks good.

What I do not understand:
Where is a description which files are available at files.gap-system.org,
and who (except GAP.jl) knows about these files and uses them?
The download links on the GAP webpages point to github.com for GAP itself, and to the URLs listed in the PackageInfo.g files for individual packages.

[fingolfin]

Looks good.

What I do not understand: Where is a description which files are available at files.gap-system.org, and who (except GAP.jl) knows about these files and uses them? The download links on the GAP webpages point to github.com for GAP itself, and to the URLs listed in the PackageInfo.g files for individual packages.

That's a very good question. It used to be that files.gap-system.org (or rather, its predecessor, which IIRC was a path under www.gap-system.org was browsable, so a user could go there and navigate around to find stuff. But we had to disable this, because site scrapers were generating many GB of traffic per day (and that was several years ago, before the AI bot scraper apocalypse). I don't think we can afford making it browsable again.

The existing structure was kinda "grandfathered in".

So, I think this is indeed something missing, and we should document this somewhere.

Note that from my POV, the main motivation to keep this around (at least initially) was to have a backup of everything: i.e. while it's good to have GitHub do the hosting for us (they use a CDN, meaning faster download speeds, and usually better reliability), if there is a catastrophic outage, we should not have all our eggs in one basket. But we initially deliberately stopped mirroring packages there when we rewrote the PackageDistro in 2022. That only came back later, and I must admit I forgot the details; perhaps it was indeed for GAP.jl? Regardless, thanks to AI, I decided it is easy enough to restore this service, so now I did.

[fingolfin]

https://files.gap-system.org now shows some information about the mirroring. This file is also in the https://github.com/gap-system/gap-files repository