xlint: do not allow $pkgname in changelog/distfiles

[hosaka]

Closes #350

[classabbyamp]

this has been a style contention between maintainers, we should probably get a wider consensus

[classabbyamp]

that said, I am in favour of this, and probably also a check for $homepage in the same variables, and check for $pkgname in homepage

[hosaka]

If it is something that prevents PRs from being merged, it should be added xlint, so the contributors get notified early on. I think there is already a scan for homepage= that does not allow any variables. I can add a $homepage check to changelog/distfiles.

[hosaka]

distfiles=${pkgname} is the most frequently used variation: https://github.com/search?q=repo%3Avoid-linux%2Fvoid-packages+%2Fdistfiles%3D.*\%24\{%3Fpkgname\}%3F%2F&type=code

[ahesford]

I agree with the prohibition on variables in changelog, because copying the URL is a useful operation on that field.

I am opposed to a prohibition on $homepage in distfiles. We already require the use of at least one variable, $version, for dynamism. Thus, the distfiles URL is never useful outside of the interpreted shell environment. In many cases, especially for GitHub sources, forced expansion in this field results in extensive repetition for no useful benefit. Although some maintainers disagree with me, I am not sure a consensus has been reached.

I have no strong opinion on prohibiting $pkgname in distfiles. It does not usually save much repetition and this level of dynamism is usually not useful.