readall: Use CLI::Parser to parse args

Library/Homebrew/cmd/readall.rb

@@ -10,19 +10,41 @@
 #:    If `--syntax` is passed, also syntax-check all of Homebrew's Ruby files.
 
 require "readall"
+require "cli_parser"
 
 module Homebrew
   module_function
 
+  def readall_args
+    Homebrew::CLI::Parser.new do
+      usage_banner <<~EOS
+        `readall` [<options>] [<taps>]
+
+        Import all formulae from specified <taps> (defaults to all installed taps).
+        This can be useful for debugging issues across all formulae when making
+        significant changes to `formula.rb`, testing the performance of loading
+        all formulae or to determine if any current formulae have Ruby issues.
+      EOS
+      switch "--aliases",
+             description: "Verify any alias symlinks in each tap."
+      switch "--syntax",
+             description: "Syntax-check all of Homebrew's Ruby files."
+      switch :verbose
+      switch :debug
+    end
+  end
+
   def readall
-    if ARGV.include?("--syntax")
+    readall_args.parse
+
+    if args.syntax?
       scan_files = "#{HOMEBREW_LIBRARY_PATH}/**/*.rb"
       ruby_files = Dir.glob(scan_files).reject { |file| file =~ %r{/(vendor|cask)/} }
 
       Homebrew.failed = true unless Readall.valid_ruby_syntax?(ruby_files)
     end
 
-    options = { aliases: ARGV.include?("--aliases") }
+    options = { aliases: args.aliases? }
     taps = if ARGV.named.empty?
       Tap
     else