cmd/go: configure -buildvcs via environment variable

[zmb3]

Would there be any appetite for an environment variable alternative that configures the -buildvcs flag?

Use case - in order to build my project with 1.18 I need to set -buildvcs=false - our repository layout breaks the "main package and the main module containing it are in the repository containing the current directory rule."

If I unconditionally set -buildvcs=false, the project builds successfully on Go 1.18, but fails on 1.17 because it doesn't understand the -buildvcs flag. In order to support both Go versions, I have to add logic to handle version-specific flags.

Something like an environment variable would allow builds on 1.17 and 1.18 to succeed.

[seankhliao]

maybe we should just backport recognizing (and ignoring) -buildvcs in GOFLAGS for 1.17

cc @bcmills @matloob

[bcmills]

I suspect that your use-case will be fixed more simply by CL 398855.

[bcmills]

@zmb3, could you have a look at #51748 and see if that will resolve your use-case?

[zmb3]

Ironically, I originally had this comment in #51478 and was concerned that would muddy the issue.

But yes, if we default to buildvcs=auto and backport that to 1.17 I would be all set.

[zmb3]

@bcmills I'm happy to close this one if there's no further action needed and -buildvcs will be backported to Go 1.17 - let me know (or just go ahead and close).

[seankhliao]

I don't think -buildvcs will be backported, only that the new default (auto) for 1.18 means you shouldn't need to set anything that may conflict between versions.

[zmb3]

Ah, I understand now. That's fine too!

[bcmills]

Duplicate of #51748