cmd/go: go get has no way to get test dependencies

[mitchellh]

What steps will reproduce the problem?

1. Create a test in your package that imports any package that you don't have downloaded
yet.
2. `go get`
3. `go test` - Fails due to import not found. 

What is the expected output?

`go get` will get the test dependencies as well, or at least have a flag to.

What do you see instead?

`go get` doesn't get any test dependencies, so the tests fail.

Which compiler are you using (5g, 6g, 8g, gccgo)?

6g

Which operating system are you using?

Mac OS X 10.8.3

Which version are you using?  (run 'go version')

1.0.3

Please provide any additional information below.

There is a workaround to this, using `go list`. You can build something like this:
https://gist.github.com/mitchellh/9655102de0bc0a849cc2

However, I feel that this is less than ideal and is counter-intuitive to the rest of the
way that Go works. I think there should be a flag on `go get` that gets test
dependencies.

[rsc]

Comment 2:

Labels changed: added priority-later, go1.2maybe, feature, removed priority-triage.

[robpike]

Comment 3:

Labels changed: added toolchange.

Status changed to Accepted.

[adg]

Comment 4:

https://golang.org/cl/12566046

Owner changed to @adg.

Status changed to Started.

[adg]

Comment 5:

This issue was closed by revision 5dde7cc.

Status changed to Fixed.