cmd/go,x/telemetry/config: collect vcs systems used

[seankhliao]

Summary

I propose we collect a count of whether each vcs system (git, hg, svn, fossil, bzr) was used recently.
I question the continued value of supporting the less used systems (e.g. bazaar, cmd/go special cases launchpad.net, but I believe it has switched primarily to git now).

Proposed Config Change

[mknyszek]

CC @golang/telemetry

[hyangah]

Alternative way to inspect this is to look into the module info proxy.golang.org see. Recognized vcs kinds are recorded there.

https://proxy.golang.org/golang.org/x/tools/gopls/@v/v0.16.2.info

Limitation of this approach however, is that proxy.golang.org sees only publicly available source code.

[seankhliao]

cmd/go defaults GOVCS to "public:git|hg,private:all". Does the proxy still handle the other vcs systems?

[hyangah]

cmd/go defaults GOVCS to "public:git|hg,private:all". Does the proxy still handle the other vcs systems?

Yes. proxy.golang.org uses public:all.

[findleyr]

We discussed this in the telemetry proposal meeting today. We'd like to put this on hold until there's a concrete proposal to deprecate support for a VCS system. We think the evidence in the proxy is probably sufficient to justify such a proposal, so there is no pressing need for telemetry data.

(And for what it's worth, we are unlikely to prioritize deprecating VCS support any time soon, since it would be a significant project).