internal: Nudge to ugprade to v2

If you are reading this, you have three choices:

- Upgrade to v2. Seriously, do this. It's so much better!
- Disable the nudge with the environment variable PANICPARSE_V1_NO_WARN=1
- Stick to v1.5.0.
I

cmd/pp/main.go

@@ -24,7 +24,7 @@ import (
 )
 
 func main() {
-	if err := internal.Main(); err != nil {
+	if err := internal.Main("/cmd/pp"); err != nil {
 		fmt.Fprintf(os.Stderr, "Failed: %s\n", err)
 		os.Exit(1)
 	}

internal/main.go

@@ -117,7 +117,7 @@ func showBanner() bool {
 // Main is implemented here so both 'pp' and 'panicparse' executables can be
 // compiled. This is to work around the Perl Package manager 'pp' that is
 // preinstalled on some OSes.
-func Main() error {
+func Main(rel string) error {
 	aggressive := flag.Bool("aggressive", false, "Aggressive deduplication including non pointers")
 	parse := flag.Bool("parse", true, "Parses source files to deduct types; use -parse=false to work around bugs in source parser")
 	rebase := flag.Bool("rebase", true, "Guess GOROOT and GOPATH")
@@ -138,6 +138,10 @@ func Main() error {
 		log.SetOutput(ioutil.Discard)
 	}
 
+	if os.Getenv("PANICPARSE_V1_NO_WARN") != "1" {
+		fmt.Fprintf(os.Stderr, "More features! Upgrade to panicparse v2 with: go get github.com/maruel/panicparse/v2%s\n", rel)
+	}
+
 	var err error
 	var filter *regexp.Regexp
 	if *filterFlag != "" {

internal/main_test.go

@@ -83,7 +83,7 @@ func TestProcessFilter(t *testing.T) {
 func TestMainFn(t *testing.T) {
 	t.Parallel()
 	// It doesn't do anything since stdin is closed.
-	if err := Main(); err != nil {
+	if err := Main(""); err != nil {
 		t.Fatal(err)
 	}
 }

main.go

@@ -24,7 +24,7 @@ import (
 )
 
 func main() {
-	if err := internal.Main(); err != nil {
+	if err := internal.Main(""); err != nil {
 		fmt.Fprintf(os.Stderr, "Failed: %s\n", err)
 		os.Exit(1)
 	}