Add an homebrew external commad for auditing head-only formula
user
```ruby
# This homebrew external command is used to override `brew audit`
# so that it will omit the HEAD only error.
#
# This file should be removed after neovim reaching stable release.

require "cmd/audit"

class FormulaAuditor
    def audit_specs
    end
end

Homebrew.audit
```
assistant