[bug#33801] import: github: Support source URIs that redirect to GitHub

[Arun Isaac <arunisaac@systemreboot.net>]

> We can use heuristics in many cases to determine whether an updater
> applies to a package; most of the time, that’s only based on the URL,
> and it might also work for many cgit instances—those that have “/cgit”
> in their URL.
>
> Then again, I expect that a growing number of packages will be obtained
> through ‘git-fetch’, and the updater for such a thing is trivial
> (interestingly it’s not yet implemented though :-)).
>
> So I feel like at present we don’t have strong evidence that that the
> simple URL-based approach would not scale.

Agreed! Better to not complicate things beyond what is necessary at this
point. I am not confident that good heuristics exist. But, if we do use
git-fetch for the majority of our packages, like you said, updating will
be trivial.

I will proceed with the lint check as discussed earlier.