packer fix: state that the command does not work for hcl files (#11238)

command/fix.go

@@ -50,6 +50,10 @@ func (c *FixCommand) ParseArgs(args []string) (*FixArgs, int) {
 }
 
 func (c *FixCommand) RunContext(ctx context.Context, cla *FixArgs) int {
+	if hcl2, _ := isHCLLoaded(cla.Path); hcl2 {
+		c.Ui.Error("packer fix only works with JSON files for now.")
+		return 1
+	}
 	// Read the file for decoding
 	tplF, err := os.Open(cla.Path)
 	if err != nil {