Add flag to fail publishing if version conflict in NPM

plugin.go

@@ -19,15 +19,16 @@ import (
 type (
 	// Config for the plugin.
 	Config struct {
-		Username   string
-		Password   string
-		Token      string
-		Email      string
-		Registry   string
-		Folder     string
-		SkipVerify bool
-		Tag        string
-		Access     string
+		Username       string
+		Password       string
+		Token          string
+		Email          string
+		Registry       string
+		Folder         string
+		SkipVerify     bool
+		FailIfConflict bool
+		Tag            string
+		Access         string
 	}
 
 	npmPackage struct {
@@ -252,6 +253,9 @@ func shouldPublishPackage(config Config, npm *npmPackage) (bool, error) {
 
 			if strings.Compare(npm.Version, value) == 0 {
 				log.Info("Version found in the registry")
+				if config.FailIfConflict {
+					return false, errors.New("Cannot publish package due to version conflict")
+				}
 				return false, nil
 			}
 		}