ref: clarify keys with examples

[liyishuai]

We should clarify many more keys e.g. I don't know how to write tested_coq_nix_versions in my meta.yml.

Also, the supported tags wiki seems outdated after coq-community/docker-base#4 (comment).

[Zimmi48]

I don't know how to write tested_coq_nix_versions in my meta.yml.

version_or_url can be either a version name already released in nixpkgs (as '8.10') or a URL of the form https://github.com/coq/coq-on-cachix/tarball/<branchname> where <branchname> can be master or a release branch like v8.12 (typically only used to test a project with branches of Coq that are still in alpha or beta.

[liyishuai]

I don't know how to write tested_coq_nix_versions in my meta.yml.

version_or_url can be either a version name already released in nixpkgs (as '8.10') or a URL of the form https://github.com/coq/coq-on-cachix/tarball/<branchname>

I can see the Cachix branch names in https://github.com/coq/coq-on-cachix/branches.
Which page lists the available versions in nixpkgs?

[Zimmi48]

On this page, at the bottom, there is the list of supported Coq versions (currently, everything between 8.5 and 8.11). The top part of the page is also interesting since it lists the currently packaged libraries that can be specified as dependencies.

[liyishuai]

I'm confused by coq_8_10 and version = "8.10.2". Which one does the version_or_url: '8.10' come from?
Feel free to push directly, since I'm not so familiar with Nix.

[Zimmi48]

The '8.10' syntax is used for convenience. It is transformed into coqPackages_8_10 in the default.nix template.

Feel free to push directly, since I'm not so familiar with Nix.

OK, let me try.

[erikmd]

LGTM, thanks @liyishuai @Zimmi48