apt-0:0.5.15cnc6-alt6.1

Although `ls' command is accepted by apt-shell, it doesn't show up by completion
(pressing tab in the prompt, or pressing tab after "l" in the prompt).

It is accepted, here is an example:

apt> ls apt*
apt                apt-conf-sisyphus  apt-rsync          aptitude           
apt-conf-Master    apt-indicator      apt-utils          
apt> 

Steps to Reproduce:
[root@tosha root]# apt-shell
Reading Package Lists... Done
Building Dependency Tree... Done
Welcome to the APT shell. Type "help" for more information.
apt> <TAB><TAB>
autoclean        dist-upgrade     quit             showpkg
build-dep        dselect-upgrade  rdepends         status
check            exit             remove           unmet
clean            help             script           update
commit           install          search           upgrade
depends          keep             show             whatdepends
apt> l<TAB>

Actual Results:  
"ls" is not in the list, and no completion are suggested for "l".