Remove base64 gem and add Homebrew/NoBase64 cop

[MikeMcQuaid]

This can now be done as all formulae which required base64 have been switched to native String#unpack1/Array#pack in Homebrew/homebrew-core#296594.

• Revert "Restore base64 gem" (Restore base64 gem #23344): removes the gem from the Gemfile and the vendored bundle again. The autogenerated RBI commit from Restore base64 gem #23344 is not reverted as it was unrelated stanza drift. base64 (0.3.0) stays in Gemfile.lock specs/checksums as a transitive dependency of the optional ruby-prof gem, matching the state before Restore base64 gem #23344.

• Add a Homebrew/NoBase64 cop so usage cannot creep back into formulae or casks. It flags require "base64" and any Base64 usage in Formula/Casks files in any tap (scoped with the same globs as Homebrew/NoFileutilsRmrf) and autocorrects simple cases to the same replacements used in Remove base64 gem requirement homebrew-core#296594:

  • require "base64" is removed
  • Base64.decode64(x) becomes x.unpack1("m")
  • Base64.strict_decode64(x) becomes x.unpack1("m0")
  • Base64.encode64(x) becomes [x].pack("m")
  • Base64.strict_encode64(x) becomes [x].pack("m0")

  Base64.urlsafe_* calls and compound expressions that would need parenthesising are flagged without autocorrection. Verified end to end on a scratch core formula: brew style reports the offences and brew style --fix applies the conversions above.

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Claude Code Fable 5 with local review and testing.

[Copilot]

Pull request overview

This PR removes Homebrew’s direct dependency on the base64 gem (now that affected formulae have migrated to native String#unpack1/Array#pack) and adds a RuboCop cop to prevent Base64 usage from reappearing in formulae/casks across taps.

Changes:

• Remove base64 from Library/Homebrew/Gemfile dependencies and delete the vendored base64 gem files.
• Add Homebrew/NoBase64 RuboCop cop (with autocorrections for common encode64/decode64 patterns) and accompanying spec.
• Wire the cop into RuboCop loading/config, and ignore vendored base64-* gem directories in .gitignore.

Reviewed changes

Copilot reviewed 5 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
Library/Homebrew/vendor/bundle/ruby/4.0.0/gems/base64-0.3.0/lib/base64.rb	Removes vendored base64 implementation file.
Library/Homebrew/vendor/bundle/ruby/4.0.0/gems/base64-0.3.0/COPYING	Removes vendored base64 licensing file.
Library/Homebrew/test/rubocops/no_base64_spec.rb	Adds tests for the new Homebrew/NoBase64 cop.
Library/Homebrew/rubocops/no_base64.rb	Introduces the Homebrew/NoBase64 cop and autocorrection logic.
Library/Homebrew/rubocops/all.rb	Ensures the new cop file is required/registered.
Library/Homebrew/Gemfile.lock	Drops base64 from direct dependency list.
Library/Homebrew/Gemfile	Removes gem "base64" from vendored gem set.
Library/.rubocop.yml	Configures Homebrew/NoBase64 include/exclude patterns and description.
.gitignore	Adds base64-* to the list of vendored gems not committed.

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[p-linnane]

Nice!