Add a function to resolve URI references relative to a base URI

[kernelmethod]

RFC 3986 Section 5.2 (https://tools.ietf.org/html/rfc3986#section-5.2) defines an method for resolving references relative to a base URI. This pull request adds the resolvereference function in order to achieve this functionality, which attempts to comply with the algorithm defined in Section 5.2.2.

Closes #18.

[fredrikekre]

I believe that this is what URIs.absuri tries to do, but this seems more general. I propose to deprecated URIs.absuri in favor of this function.

This will also close JuliaWeb/HTTP.jl#435 and JuliaWeb/HTTP.jl#626 and maybe #21 ?

[quinnj]

LGTM!

[kernelmethod]

Thanks for the review @fredrikekre, I've applied the changes you've suggested

Edit: also, I've tried the example from #21 and I've confirmed that using resolvereference will get the expected result, so this should close that issue too.

[fredrikekre]

I've tried the example from #21 and I've confirmed that using resolvereference will get the expected result, so this should close that issue too.

But only if you used resolvereference instead of joinpath, right? Perhaps joinpath should be updated to call resolvereference?

[kernelmethod]

But only if you used resolvereference instead of joinpath, right?

Yes, correct.

Perhaps joinpath should be updated to call resolvereference?

Possibly? resolvereference and joinpath are quite similar in their purpose (as I noted in #18), but resolvereference explicitly complies with RFC 3986 Sec. 5.2 (and hence with URI resolution methods in other languages, including the JavaScript example from #21). It'd probably be nice if joinpath called resolvereference under the hood, but I'm not sure if there's a way to do so that doesn't break the current behavior of joinpath.

If we aren't worried about breaking joinpath's behavior, though, we could probably very easily redefine it as

Base.joinpath(base::URI, parts...) = reduce(resolvereference, [base, parts...])

(or something similar).