Introduce and use a meta file format for URLs and available versions

[hasufell]

Fixes #21
Fixes #9
Fixes #10
Fixes #5

Not supposed to be merged right now since it's not clear where we want to host those meta info files.

Files are currently here: https://gist.github.com/hasufell/71bf6cf0d3606d5b9a71c633940610bf

[hasufell]

TODO:

• outline how to add distros for contributors
• maybe write a test for uniqueness of some tags (e.g. "unknown" in download-urls has to be unique for a combination of tool-arch-ver, recommended in available-versions has to be unique for tool)
• avoid redundant downloads (timestamp?) (not very worthwile it seems: https://stackoverflow.com/questions/50194241/get-when-the-file-was-last-updated-from-a-github-repository)

[hasufell]

I'm not sure allowing full control over downloader is a good thing. Maybe this should rather be a simple switch.

[hvr]

I still think that using a gist to host the metadata is not a good idea, as it makes it harder for people contribute to the metadata via GitHub PRs nor is it integrated well with the GitHub issue tracker workflow.

[hasufell]

The gist is only temporary, so I can test changes more easily.

[hasufell]

If there is no further comment, then I will merge this soon.

[hvr]

I tried this on a macOS box, and this made me realise that the metadata files seem to imply Linux as the OS; imo, we either need to encode the OS (linux, windows, darwin, freebsd, ...) as separate dimension, or we need to account for different per-OS flavours of "unknown" distributions (e.g. linux-unknown);

btw, some prior art exists in Autoconf's target triples:

Autoconf-generated configure scripts can make decisions based on a canonical name for the system type, or target triplet, which has the form: cpu-vendor-os, where os can be ‘system’ or ‘kernel-system’

where you typically have something like

• x86_64-unknown-linux
• x86_64-unknown-linux-gnu (kernel = Linux, system = GNU)

but that's not ideal for ghcup either, as it doesn't include the distro name/release

there's also https://wiki.debian.org/Multiarch/Tuples which shows the extent of the configuration space possible even with only just Debian.

[hasufell]

I don't think it's necessary to delay this further. Mac support can be done in a later PR. The file format is versioned.

…

On October 30, 2018 11:30:00 AM UTC, Herbert Valerio Riedel ***@***.***> wrote: I tried this on a macOS box, and this made me realise that the metadata files seem to imply Linux as the OS; imo, we either need to encode the OS (linux, windows, darwin, freebsd, ...) as separate dimension, or we need to account for different per-OS flavours of "`unknown`" distributions -- You are receiving this because you authored the thread. Reply to this email directly or view it on GitHub: #28 (comment)

[hvr]

fine by me; this PR certainly doesn't make things worse than before :-)