Add an option to specify build plan download address.

[TerrorJack]

Currently, stack downloads stackage build plans from s3.amazonaws.com. Unfortunately, in many areas in China, this domain is blocked due to the Great Firewall (national network censoring system).

So I'm proposing that stack add an option to specify build plan download address. This allows us to set up a stackage mirror along existing hackage mirrors in China, and Chinese Haskellers won't have to endure Internet connection issues in their workflow. Thank you!

[mgsloan]

Yeah, this would be good. Looks like the following URLs contain amazonaws.com:

So I suppose the solution here would be to allow configuration of something other than https://s3.amazonaws.com. Something like metadata-mirror: ... in yaml configuration.

Is github also affected? We also download things from github.

[TerrorJack]

Yes, github is also affected.

[mgsloan]

I see. I suppose we could have something like:

stack-urls:
    snapshots: https://s3.amazonaws.com/haddock.stackage.org/snapshots.json
    index: https://s3.amazonaws.com/hackage.fpcomplete.com/00-index.tar.gz"
    # etc

Alternatively, we could make it so that you can download some set of files and use those locally (see also #1594 ).

[igrep]

I wonder whether package-indices and latest-snapshot-url is not for you...?

I'm also very interested in this topic.

[TerrorJack]

@igrep package-indices affects Hackage indices/packages only; latest-snapshot-url won't do much good, since it's only used when stack needs to find a latest LTS/nightly, and does not affect how stack fetches a build plan.

[igrep]

To make it clear, it is rawGithubUrl that you want to make configurable, right?

As long as I checked, it's actually used to download build plans
and any other URLs stack uses seem to be configurable via package-indices, latest-snapshot-url, and --stack-setup-yaml.

[TerrorJack]

@igrep Right.