warn on templates in libraries that will be skipped

pkg/lint/rules/template.go

@@ -99,6 +99,9 @@ func Templates(linter *support.Linter, values map[string]interface{}, namespace
 	for _, template := range chart.Templates {
 		fileName, data := template.Name, template.Data
 		fpath = fileName
+        if chart.Metadata.Type == "library" {
+            linter.RunLinterRule(support.WarningSev, fpath, validateLibraryTemplate(fileName))
+        }
 
 		linter.RunLinterRule(support.ErrorSev, fpath, validateAllowedExtension(fileName))
 		// These are v3 specific checks to make sure and warn people if their
@@ -179,6 +182,13 @@ func validateTopIndentLevel(content string) error {
 	return scanner.Err()
 }
 
+func validateLibraryTemplate(fileName string) error {
+    if fileName[0] != '_' {
+        return fmt.Errorf("template file name %s does not start with '_' character", fileName)
+    }
+    return nil
+}
+
 // Validation functions
 func validateTemplatesDir(templatesPath string) error {
 	if fi, err := os.Stat(templatesPath); err != nil {