Install GHC from file

[cblp]

Implements #2224.

Should I write tests?

[mgsloan]

Thanks for working on this!

[mgsloan]

Why not allow setting content-length and sha1 for local files? This way you could potentially test the stack.yaml configuration before uploading, and not need to test downloading.

Also, other places that use chattyDownload could benefit from this as well. While it's an unlikely case, you could specify your own 7zip version for example.

I guess the resolution of this would be to have chattyDownload and verifiedDownload take a Either (Path Abs File) DownloadRequest, and return a Path Abs File for the local location of the file.

I realize that's a fair bit of refactoring atop this. I can go ahead and merge if you don't want to do that (and probably get around to it myself at some point)

[cblp]

Why not allow setting content-length and sha1 for local files? This way you could potentially test the stack.yaml configuration before uploading, and not need to test downloading.

OK, I'm removing warnings about them.

[cblp]

I didn't change chattyDownload, because downloading to specified path is strange — it is actually copying and it's always better to use file from original location on disk than copying it to another directory. Or not always?

[mgsloan]

Right, we'd want to call it something different. I understand why you didn't make the change that way, it would be larger.

I don't think that this verification stuff should be coupled with downloading and should be split up. I can worry about that decoupling, though.

[mgsloan]

Merged! Sorry for letting this languish.

[cblp]

Thanks!