build and deploy ePub e-book files

[das-g]

See a run of these actions here.

Results available from https://das-g.github.io/django-girls-tutorial/book_<lang>.epub, e.g. for English https://das-g.github.io/django-girls-tutorial/book_en.epub

Before merging this, we'll probably want to have more meaningful file names, e.g. django-girls-tutorial_en.epub.

Results available from https://das-g.github.io/django-girls-tutorial/django-girls-tutorial_<lang>.epub, e.g. for English https://das-g.github.io/django-girls-tutorial/django-girls-tutorial_en.epub

closes #1785

[ekohl]

I wonder how people discover we have these. Is there anything that links to it?

[ekohl]

I had not seen this action before. I'm not sure how much the cache really saves, but I do like the style

[das-g]

I used it so I don't have to remember how to make apt well-behaved for non-interactive use. From the top of my head, that'd at least involve

• use old apt-get commands instead of the new apt ones
• call apt-get update before apt-get install, as otherwise the packages might not be known
• use -y option for both these commands
• set environment variable DEBIAN_FRONTEND to noninteractive before all that

I haven't known this action before either, but seen it recommended in this Stack Overflow answer to the question How to apt-get install in a GitHub Actions workflow?.

[ekohl]

Is it needed to specify a version? Reading through the source I see this is the cache version, not the calibre version. I'd suggest to drop it and only add it once we need it. You can also purge caches via the UI nowadays so it's not needed as much anymore.

[das-g]

Is there anything that links to it?

Not yet. But https://github.com/DjangoGirls/tutorial/blob/master/LANGS.md?plain=1 has the paths to the HTML versions of the various translations hardcoded anyway, so I guess we could also include hardcoded links to the ePub files?

[ekohl]

I think that's a good idea.