feat: new linter exclusions system

[ldez]

This PR is a part of the v2: #5300

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Important

This PR deliberately omits documentation about the new options and section (but the JSONSchema is updated).
This is because I don't want to deprecate the previous section for now: I think it is better to handle that when all the v2 proposals are managed to avoid multiple migrations.

The main goal is to replace issue.exclude-xxx options with linters.exclusions section.

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There is a new option linters.exclusions.warn-unused that emits a warning if a linters.exclusions.rules or linters.exclusions.paths is unused.

There is a new option run.relative-path-mode with 4 modes:

• gomod: paths are relative to the go.mod
• gitroot: paths are relative to the git root.
• cfg: paths are relative to the configuration position.
• wd (v1 default): paths are relative to the location where golangci-lint is run.

This option controls all the path-related options:

• issues.exclude-rules[].path
• issues.exclude-rules[].path-except
• issues.exclude-dirs
• issues.exclude-files
• severity.rules[].path
• severity.rules[].path-except
• custom[].path
• linters.exclusions.paths
• linters.exclusions.paths-except
• linters.exclusions.rules[].path
• linters.exclusions.rules[].path-except
• linters

The linter configuration related to paths should use the placeholder ${base-path}:

• gocritic (gocritic.ruleguard.rules)
• depguard (rules[].files)
• goheader (goheader.template-path)

errcheck: the option errcheck.exclude has been deprecated since golangci-lint v1.42 so I didn't add the support of the placeholder.

With the new option run.relative-path-mode, you can now run golangci-lint inside a package and the configuration related to file paths will work.

In v2, output.path-prefix will be used only for output and not for matching, and the default relative path mode will be gomod or cfg (not wd like today).

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More details about the topic are inside the issues:

• 🌟 Let's talk about exclusion options inside issues section #5297
• 🌟 Let's talk about default exclusions #5298

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configuration overview

linters:
  # ...
  
  exclusions:
    presets:
      - comments
      - stdErrorHandling
      - commonFalsePositives
      - legacy
    generated: strict
    warn-unused: true
    rules:
      - path: _test\.go
        linters:
          - gocyclo
          - errcheck
          - dupl
          - gosec
      - path-except: _test\.go
        linters:
          - forbidigo
      - path: internal/hmac/
        text: "weak cryptographic primitive"
        linters:
          - gosec
      - linters:
          - staticcheck
        text: "SA9003:"
      - linters:
          - lll
        source: "^//go:generate "
    paths:
      - src/external_libs
      - autogenerated_by_my_lib
      - ".*\\.my\\.go$"
      - lib/bad.go
    paths-except:
      - '^base/a/.+'

---

Fixes #5297
Related to #5298
Fixes #4635
Fixes #3953
Fixes #3717
Fixes #1178
Closes #3748

[ldez]

@bombsimon @alexandear Can I do something to ease the review?

[bombsimon]

@bombsimon @alexandear Can I do something to ease the review?

Sorry for slow review! I don't think so, mostly just ben busy and given your very thorough research on this topic in the issue (thanks for that amazing work) I wanted to also catch up with all your findings to better understand these changes.

I'll try to get to this asap during the week!

[bombsimon]

LGTM, good stuff!

[ldez]

I'm so excited to merge this PR, I know this is mainly internals but I spend a lot of time on it, and the next PR (I will open it 1 minute after the merge of this one) will add the fmt command 🎉

[ldez]

I will press the merge button 🎉