add line to activate bash_completion for given script_name into dest

        You can use this for letting the user install bash_completion::

            from argdeco import command, main

            @command("install-bash-completion",
                arg('--dest', help="destination", default="~/.bashrc")
            )
            def install_bash_completion(dest):
                main.install_bash_completion(dest=dest)

def install_bash_completion(self, script_name=None, dest="~/.bashrc"):
        '''add line to activate bash_completion for given script_name into dest

        You can use this for letting the user install bash_completion::

            from argdeco import command, main

            @command("install-bash-completion",
                arg('--dest', help="destination", default="~/.bashrc")
            )
            def install_bash_completion(dest):
                main.install_bash_completion(dest=dest)

        '''
        if 'USERPROFILE' in os.environ and 'HOME' not in os.environ:
            os.environ['HOME'] = os.environ['USERPROFILE']
        dest = expanduser(dest)
        if script_name is None:
            script_name = sys.argv[0]

        self.uninstall_bash_completion(script_name=script_name, dest=dest)
        with open(dest, 'a') as f:
            f.write('eval "$(register-python-argcomplete %s)"\n' % script_name)