improve description

builder/docker/driver_docker.go

@@ -303,7 +303,8 @@ func (d *DockerDriver) TagImage(id string, repo string, force bool) error {
 		}
 	} else {
 		// do nothing if Docker version >= 1.12.0
-		log.Printf("[WARN] force is removed since Docker 1.12.0")
+		log.Printf("[WARN] option: \"force\" will be ignored here")
+		log.Printf("since it was removed after Docker 1.12.0 released")
 	}
 	args = append(args, id, repo)
 

website/source/docs/post-processors/docker-tag.html.md

@@ -33,7 +33,7 @@ repository is required.
 
 -   `force` (boolean) - If true, this post-processor forcibly tag the image even
     if tag name is collided. Default to `false`.
-    But it will be ignore if Docker version greater or equal than 1.12.0,
+    But it will be ignored if Docker >= 1.12.0 was detected,
     since the `force` option was removed after 1.12.0. [reference](https://docs.docker.com/engine/deprecated/#/f-flag-on-docker-tag)
 
 ## Example