go.mod: List our own tools in the "tools" directive

We previously adopted the new "tools" mechanism for the third-party tools
we use for go:generate, etc. However, it's also acceptable to include tools
from our own module in this list, which then makes it possible to run them
using the same "go tool" shorthand.

For example, it's now possible to run "go tool protobuf-compile" to rebuild
the protocol buffers schemas, or "go tool tofu" as a shorthand way to
compile and run OpenTofu CLI itself.

It still remains possible to run these tools in the same ways they used to
work. This is just a new way to get the same results through a more modern
Go toolchain feature.

Signed-off-by: Martin Atkins <mart@degeneration.co.uk>

Makefile

@@ -44,7 +44,7 @@ generate:
 # versions of protoc and the protoc Go plugins.
 .PHONY: protobuf
 protobuf:
-	go run ./tools/protobuf-compile .
+	go tool protobuf-compile .
 
 # Golangci-lint is installed first and then run twice to cover all platforms.
 .PHONY: golangci-lint

go.mod

@@ -324,6 +324,10 @@ replace github.com/hashicorp/hcl/v2 v2.20.1 => github.com/opentofu/hcl/v2 v2.20.
 tool (
 	github.com/hashicorp/copywrite
 	github.com/mitchellh/gox
+	github.com/opentofu/opentofu/cmd/tofu
+	github.com/opentofu/opentofu/tools/find-dep-upgrades
+	github.com/opentofu/opentofu/tools/loggraphdiff
+	github.com/opentofu/opentofu/tools/protobuf-compile
 	go.uber.org/mock/mockgen
 	golang.org/x/tools/cmd/stringer
 	google.golang.org/grpc/cmd/protoc-gen-go-grpc

tools/protobuf-compile/protobuf-compile.go

@@ -69,7 +69,7 @@ var protocSteps = []protocStep{
 
 func main() {
 	if len(os.Args) != 2 {
-		log.Fatal("Usage: go run github.com/opentofu/opentofu/tools/protobuf-compile <basedir>")
+		log.Fatal("Usage: go tool protobuf-compile <basedir>")
 	}
 	baseDir := os.Args[1]
 	workDir := filepath.Join(baseDir, "tools/protobuf-compile/.workdir")