--mount=type=cache 和普通的docker构建缓存有何不同?

Question

使用了--mount=type=cache和不使用都可以使用构建缓存，所以--mount=type=cache的真实作用是什么呢

不使用 --mount=type=cache

Uploading context 18.829 MB
Uploading context
Step 1/2 : FROM busybox
 ---> 769b9341d937
Step 2/2 : CMD echo Hello world

---> Using cache

---> 99cc1ad10469
Successfully built 99cc1ad10469
$ echo ".git" > .dockerignore
$ docker build .
Uploading context  6.76 MB
Uploading context
Step 1/2 : FROM busybox
 ---> 769b9341d937
Step 2/2 : CMD echo Hello world
 ---> Using cache
 ---> 99cc1ad10469
Successfully built 99cc1ad10469

使用了 --mount=type=cache

# syntax = docker/dockerfile:1.2
FROM golang
...
RUN --mount=type=cache,target=/root/.cache/go-build go build ...

buildkit docs