A simple script that allows prefix-based searching of a locally cached copy of
all available PyPi packages, a la apt-cache pkgnames. The cache is created and
updated manually by calling pip-cache update, in the spirit of
apt-get update.
The cache is stored in $XDG_DATA_HOME/pip-cache/all-packages.txt, where
$XDG_DATA_HOME is usually ~/.local/share on Linux systems.
Used in pip-bash-completion.