go 1.0.x support

[mreiferson]

Unfortunately, due to the dependency on code.google.com/p/go.tools/go/vcs, godep cannot be built w/ go versions prior to 1.1.

$ go get github.com/kr/godep
# code.google.com/p/go.tools/go/vcs
../../../code.google.com/p/go.tools/go/vcs/discovery.go:20: function ends without a return statement
../../../code.google.com/p/go.tools/go/vcs/discovery.go:31: function ends without a return statement

I'm not sure if it was your intention to support only go 1.1+, but it would be nice if this was usable on the lowest common denominator.

It's unlikely that they'll accept a patch to resolve the above issues, and it seems like it is just used to detect what VCS each import uses, right? Would you consider a patch which eliminates this external dependency so that godep can be used with older go installations?

[mreiferson]

or perhaps build tags to support an older implementation for go1.0.x?

[mreiferson]

FYI, I took a shot to see if we can get upstream to resolve this:

https://codereview.appspot.com/14283043/

[mreiferson]

closing, got that CL merged

[mreiferson]

I spoke too soon, this needed one minor tweak.

[mreiferson]

@kr any thoughts on this change?

[kr]

This looks great. I don't want to reimplement package vcs.
We use it for a few things:

• detect which VCS to use
• find the repo root
• find the remote url

Doing these things correctly means matching the go tool's
behavior, including everything described in go help remote.