176       cmd_name = args.shift.downcase
177       cmd = find_command cmd_name
182   def find_command(cmd_name)  argument
183     cmd_name = find_alias_command cmd_name
185     possibilities = find_command_possibilities cmd_name
189             "Ambiguous command #{cmd_name} matches [#{possibilities.join(', ')}]"
191       raise Gem::CommandLineError, "Unknown command #{cmd_name}"
197   def find_alias_command(cmd_name)  argument
198     alias_name = ALIAS_COMMANDS[cmd_name]
199     alias_name ? alias_name : cmd_name
202   def find_command_possibilities(cmd_name)  argument
203     len = cmd_name.length
205     found = command_names.select { |name| cmd_name == name[0, len] }
207     exact = found.find { |name| name == cmd_name }