feat: add verify command

[ldez]

This PR adds a new command config verify.

This command allows to verify a configuration file against a JSON Schema.

The JSON schema is obtained based on this approach:

• there is a version -> it uses https://golangci-lint.run/jsonschema/golangci.v<major>.<minor>.jsonschema.json
• there is a commit hash/revision -> it uses https://raw.githubusercontent.com/golangci/golangci-lint/<commit>/jsonschema/golangci.next.jsonschema.json
• there is no valid information -> error

The make target website_copy_jsonschema has been modified to create https://golangci-lint.run/jsonschema/golangci.v<major>.<minor>.jsonschema.json.

Fixes #2645

---

Why we will not use JSON Schema to validate .golangci.reference.yml or .golangci.next.reference.yml?

.golangci.reference.yml and .golangci.next.reference.yml are invalid by nature: they contain the exhaustive list of options but those options can be incompatible.

$ go run ./cmd/golangci-lint config verify -c .golangci.next.reference.yml --schema ./jsonschema/golangci.next.jsonschema.json
jsonschema: linters-settings.goheader does not validate with /properties/linters-settings/properties/goheader/oneOf: valid against schemas at indexes 0 and 1
jsonschema: linters-settings.custom.example does not validate with /properties/linters-settings/properties/custom/patternProperties/%5E.%2A$/oneOf: valid against schemas at indexes 0 and 1

Same thing for the configuration loading:

$ go run ./cmd/golangci-lint run -c .golangci.next.reference.yml                                       
ERRO [linter] thelper: at least one option must be enabled 
exit status 3

How many versions of the JSON schema we will support?

The build of golangci-lint using a specific official commit will use the schema related to its commit (https://raw.githubusercontent.com/golangci/golangci-lint/<commit>/jsonschema/golangci.next.jsonschema.json).

For the "real" versions, for now, we will support only the current stable version.

The system has been made to support more versions if needed: if a schema is inside the directory jsonschema/ it will be published as the other schema.
If we want to follow this way, I think we should limit the support to the 2 latest stable versions.

Why we don't embed the JSON Schema?

The usage of remote JSON schema allows us to fix the schema without releasing golangci-lint.

I think IDEs or text editors, that use JSON schema, will be always better than a command line to quickly identify syntax errors.
It is not worth to increase the binary size only for a niche.

[ldez]

@Antonboom do you have an opinion about this one?

[Antonboom]

@Antonboom do you have an opinion about this one?

🙏 I try to review as soon as possible

Let's consider the feature with validator in golangci website, like

• https://envoylint.com/
• https://docs.gitlab.com/ee/ci/lint.html
• https://config.travis-ci.com/explore
• ...

[ldez]

Let's consider the feature with validator in golangci website

Before doing that the website should be changed.
I'm not sure about the additional value for golangci-lint: the links you provided are mainly related to tools that users don't have on their computers. golangci-lint is installed and runs on computers.

🙏 I try to review as soon as possible

Sorry, I never know if anyone has seen a PR or not, so I friendly ping, I don't want to be too pushy.