feature: add boilerplate check script

[SataQiu]

Ⅰ. Describe what this PR did

1. add boilerplate check script (for go files)
2. complete all detected missing boilerplate
3. ignore generated files

Ⅱ. Does this pull request fix one issue?

Ⅲ. Why don't you add test cases (unit test/integration test)? (你真的觉得不需要加测试吗？)

Ⅳ. Describe how to verify it

./hack/check.sh

Ⅴ. Special notes for reviews

Next Steps:

1. add update-boilerplate script
2. add this check into CircleCI

[pouchrobot]

We found this is your first time to contribute to Dragonfly, @SataQiu
👏 We really appreciate it.
Just remind that you have read the contribution guide: https://github.com/dragonflyoss/Dragonfly/blob/master/CONTRIBUTING.md
If you didn't, you should do that first. If done, welcome again and please enjoy hacking! 🍻

[SataQiu]

/assign @allencloud

[allencloud]

That is so good. I like it very much. Thanks so much. I will review this asap. @SataQiu 👏

[allencloud]

Dragonfly (new-807) $ git ls-files | xargs go run ./hack/boilerplate/check-boilerplate.go
Dragonfly (new-807) $ echo $?
0
version (new-807) $ vi version/version.go
Dragonfly (new-807) $ git ls-files | xargs go run ./hack/boilerplate/check-boilerplate.go
error validating "version/version.go": the file is missing a boilerplate
exit status 1

It works with the check file.

While I am afraid that make check fails since there is no docker daemon installed on my machine. I think make file should be friendly with developer's local machine, like windows, mac and so on. And there is no need to depend on the docker engine.

[SataQiu]

Yes. I am also curious whether the ./hack/check-docker.sh can be stripped out from make check.
But hack/check.sh is OK, right?

check:
	@echo "Begin to check code formats."
	./hack/check.sh
	@echo "Begin to check dockerd whether is startup"
	./hack/check-docker.sh
.PHONY: check

[allencloud]

whether the ./hack/check-docker.sh can be stripped out from make check.

I think we should strip that from make check.

hack/hack.sh is OK.

[allencloud]

LGTM, but I think we should make it work in the integration test of travis.

[SataQiu]

LGTM, but I think we should make it work in the integration test of travis.

@allencloud
IMO, travis only runs docker-build, do you mean to add some checks, like boilerplate-check in circleci?
How about do that in another PR? That will change circleci's behavior.

[allencloud]

LGTM, I would like to merge this first. And then we can keep moving on to polish the check scripts to fit travisCI. Thanks for your work again. @SataQiu