Bug#547599: apt-cache pkgnames has a bad man note, it shows all packages not just the ones in the system

[René Mérou <ochominutosdearco@gmail.com>]

Package: apt
Version: 0.7.23.1
Severity: minor

The man says this:  

pkgnames [ prefix ] 
 This command prints the name of each package in the system. 

In spanish traslation of the man:
pkgnames [ prefijo ]
 Esta orden muestra el nombre de todos los paquetes instalados en el sistema.


But its not true like shows this examples of dpgk -l and apt-cache pkgnames:

# dpkg -l rip
No se ha encontrado ningún paquete que corresponda con rip.   
[no package found that mates with rip]

# apt-cache pkgnames rip
ripole
ripit
ripperx


Its obvious,  dpgk -l list just the installed packages but the apt-cache pkgnames shows all the packages avaliable, not just the installed ones.
And thats normal if we want to be able to use apt-cache pkgnames to use the output for use in a shell tab complete function like says the man.

So, it says "This command prints the name of each package in the system."  and it must say something like 
"This command prints the name of all the avaliable packages." 


-- Package-specific info:

-- (no /etc/apt/preferences present) --


-- (/etc/apt/sources.list present, but not submitted) --


-- System Information:
Debian Release: squeeze/sid
  APT prefers unstable
  APT policy: (500, 'unstable')
Architecture: amd64 (x86_64)

Kernel: Linux 2.6.30-1-amd64 (SMP w/2 CPU cores)
Locale: LANG=es_ES.UTF-8, LC_CTYPE=es_ES.UTF-8 (charmap=UTF-8) (ignored: LC_ALL set to es_ES.UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages apt depends on:
ii  debian-archive-keyring        2009.01.31 GnuPG archive keys of the Debian a
ii  libc6                         2.9-26     GNU C Library: Shared libraries
ii  libgcc1                       1:4.4.1-4  GCC support library
ii  libstdc++6                    4.4.1-4    The GNU Standard C++ Library v3

apt recommends no packages.

Versions of packages apt suggests:
pn  apt-doc                   <none>         (no description available)
ii  aptitude                  0.4.11.11-1+b2 terminal-based package manager
ii  bzip2                     1.0.5-3        high-quality block-sorting file co
ii  dpkg-dev                  1.15.4         Debian package development tools
ii  lzma                      4.43-14        Compression method of 7z format in
ii  python-apt                0.7.13.3       Python interface to libapt-pkg
ii  synaptic                  0.62.9         Graphical package manager

-- no debconf information