$ cd fmt
$ go vet -x
/Users/r/go/pkg/tool/darwin_amd64/vet doc.go export_test.go fmt_test.go format.go
print.go scan.go scan_test.go stringer_test.go
$ # Add the -v flag
$ /Users/r/go/pkg/tool/darwin_amd64/vet -v doc.go export_test.go fmt_test.go format.go
print.go scan.go scan_test.go stringer_test.go

see lots of incorrect errors because:

vet: fmt_test.go:5:1: package fmt_test; expected fmt

$ # Do this instead, breaking the arguments into two runs of distinct packages.
$ # The warnings here are legitimate.
$
$ /Users/r/go/pkg/tool/darwin_amd64/vet -v doc.go export_test.go format.go print.go
scan.go
Checking file doc.go
Checking file export_test.go
Checking file format.go
Checking file print.go
print.go:229: can't check non-constant format in call to Fprintf
print.go:244: can't check non-constant format in call to Sprintf
Checking file scan.go
$ /Users/r/go/pkg/tool/darwin_amd64/vet -v fmt_test.go scan_test.go stringer_test.go
vet: fmt_test.go:957:6: undeclared name: IsSpace
Checking file fmt_test.go  ##### This one is problematic; it's in export_test.go in
package fmt.
fmt_test.go:522: can't check non-constant format in call to Sprintf
fmt_test.go:596: can't check non-constant format in call to Sprintf
fmt_test.go:724: can't check non-constant format in call to Sprintf
fmt_test.go:748: can't check non-constant format in call to Sprintf
fmt_test.go:859: can't check non-constant format in call to Sprintf
fmt_test.go:912: can't check non-constant format in call to Sprintf
fmt_test.go:968: arg nil for printf verb %s of wrong type: untyped nil
Checking file scan_test.go
Checking file stringer_test.go
$

The question is, who should do this breakdown?