feat: allow being invoked as helm2 or helm3 in addition to helm

In transparent wrapping mode, Helm Sops binary could be named 'helm', the Helm binary being renamed to '_helm'. This didn't allow coinstalling Helm 2 and Helm 3. Helm Sops binary can now have a link named helm2 (or helm3) pointing to it to transparently wrap Helm 2 and Helm 3, the Helm 2 binary being renamed to '_helm2' (or the Helm 3 binary being renamed to '_helm3').

main.go

@@ -28,13 +28,16 @@ func runHelm() (errs []error) {
 	var helmPath string
 	var err error
 
-	if path.Base(os.Args[0]) == "helm" {
-		helmPath, err = exec.LookPath("_helm")
+	switch executableName := path.Base(os.Args[0]); executableName {
+	case "helm", "helm2", "helm3":
+		executableName = fmt.Sprintf("_%s", executableName)
+
+		helmPath, err = exec.LookPath(executableName)
 
 		if err != nil {
-			return append(errs, fmt.Errorf("failed to find Helm binary '_helm'"))
+			return append(errs, fmt.Errorf("failed to find Helm binary '%s'", executableName))
 		}
-	} else {
+	default:
 		helmPath, err = exec.LookPath("helm")
 
 		if err != nil {