list: support --full-name

Closes Homebrew/homebrew#29716.

Library/Homebrew/cmd/list.rb

@@ -1,4 +1,5 @@
 require "metafiles"
+require "formula"
 
 module Homebrew
   def list
@@ -16,8 +17,21 @@ module Homebrew
     if ARGV.include? '--pinned' or ARGV.include? '--versions'
       filtered_list
     elsif ARGV.named.empty?
-      ENV['CLICOLOR'] = nil
+      if ARGV.include? "--full-name"
-      exec 'ls', *ARGV.options_only << HOMEBREW_CELLAR
+        full_names = Formula.installed.map(&:full_name).sort do |a, b|
+          if a.include?("/") && !b.include?("/")
+            1
+          elsif !a.include?("/") && b.include?("/")
+            -1
+          else
+            a <=> b
+          end
+        end
+        puts_columns full_names
+      else
+        ENV['CLICOLOR'] = nil
+        exec 'ls', *ARGV.options_only << HOMEBREW_CELLAR
+      end
     elsif ARGV.verbose? or not $stdout.tty?
       exec "find", *ARGV.kegs.map(&:to_s) + %w[-not -type d -print]
     else