Support common source archive formats

[iand]

I proposed this in the Go issue tracker as golang/go#19614 but it was put on hold pending a solution from dep. Since that's likely to be in the medium to long term I thought I'd better open this as a tracking issue so it doesn't get lost.

Summary from that issue:

Currently the go get command expects to interact with a source control system to check out source code. There is no way to package up a source archive (e.g. tar or zip) and use go get to retrieve this.

This proposal would modify the go tool to look for a source archive according to a to-be-defined scheme when the user types go get package. The go tool would download and unpack the source archive in the correct location. Alternatively the go tool could be modified to keep the archive file and support reading source from the archive directly during a build.

[sdboyer]

I was actually just thinking about this over the weekend. Specifically, what a tar archive might look like (the need for supporting alternate source types has been clear to me for a long time). There's a ton of value in doing this, to the point that it might even be necessary for some possible long term changes - for example, the source cache in my current big-picture sketch.

This hasn't been on my immediate TODO list because we have more pressing problems, but if it's something you're interested in working on, I'd love to help you work out a spec.

[iand]

I'll work on an initial draft of a spec for discussion.

[sdboyer]

Aaaaawesome. If you're able to take into consideration some of the issues raised in the aforelinked gist, as well as have a look over #121, that should cover many of the concerns I think relevant, and might make discussion of an initial draft more productive.

I'm also happy to hop on voice/vid to discuss anytime, if you'd find that helpful!

[sdboyer]

How's this going?

[sdboyer]

gonna close this out - feel free to reopen if you find time to write up the spec!

[aajtodd]

This feels like it would be very useful, perhaps consider re-opening for better visibility if someone looking to contribute picks it up?

[iand]

I'm still interested in the topic, but no actual time to work on it right now so it'd be great if someone else were able to progress it.