treewide: interpolate src.rev into meta.changelog instead of version

[lolbinarycat]

in the process of mass checking nixpkgs metadata url, i see a few very common classes of errors:

1. pointing to blob/${version} instead of blob/v${version}
2. switching from a stable to unstable versioning scheme, and not updating the changelog url
3. using a more precise versioning scheme than the one used upstream for tags.

all of these would be fixed by interpolating src.rev (which will be either a commit or tag) instead of version (which often uses a nixpkgs-specific format)

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[dotlambda]

I agree. But this might not work if the changelog refers to GitHub release notes where refs/tags/v${version} doesn't work.

[lolbinarycat]

hmm, fair point, although i think it should be fine to just not use the fully-qualified ref name in that case? just do rev = "v${version}"?

[lolbinarycat]

although, release notes won't work for a commit either. maybe it would be better to just link to https://github.com/ORG/REPO/releases/ instead of trying to link to a specific release?

although, it will be much less important once nixpkgs metadata is tested automatically.

[Pandapip1]

See related discussion at #336454