The Go team has started the process of replacing the old "// +build" constraints with the new "//go:build" constraints. See the design doc for more details here:

https://go.googlesource.com/proposal/+/master/design/draft-gobuild.md

What is relevant is that in Go 1.17, gofmt now synchronizes the two styles. In particular, if gofmt is run against a deepcopy generated file, it will add a new "//go:build" constraint.

See https://golang.org/doc/go1.17#gofmt for details.

This issue to track making it so that zz_generated.deepcopy.go does not change when run under gofmt.