Support bikeshed include files.

[frivoal]

https://api.csswg.org/bikeshed/ and https://github.com/tobie/pr-preview/ are a great combo, except that in addition to my index.bs file, I have local custom *.include files, and if these don't stay together with the spec, the result isn't the intended one.

(cc @plinss) https://api.csswg.org/bikeshed/ should be patched to allow uploading multiple files so that I can do something like:

curl https://api.csswg.org/bikeshed/ -F file=@index.bs -F file=@header.include file=@footer.include -F force=1 > index.html

Then https://github.com/tobie/pr-preview/ should be updated to support that.

[jyasskin]

I'm doing this in 3 parts:

• Support include files in Bikeshed and ReSpec. #60 has PR-Preview scan for includes accurately.
• Teach Bikeshed to accept a URL as its input source. speced/bikeshed#1671 has Bikeshed accept a URL on its command line in addition to a local file, so it can fetch includes relative to that URL.
• A change to https://hg.csswg.org/dev/bikeshed-web will have it pass the URL to bikeshed instead of fetching it and passing the file.

[tobie]

Note that now that we’ve collected the array of urls for the includes, we can also pass them as part of the query parameters if that’s easier to implement in bikeshed.

[jyasskin]

It was easier for Bikeshed to just look things up relative to the input URL.

@frivoal, your use case is going to require you to list the custom boilerplate files in the Local Boilerplate metadata.

[jyasskin]

Success! https://pr-preview.s3.amazonaws.com/jyasskin/privacy-threat-model/pull/30.html#model-cross-site-recognition

Thanks everyone (@tobie, @plinss, @tabatkins, @marcoscaceres, @sidvishnoi) for the design help and reviews!

[tobie]

This is so awesome! Congrats!!