commitpkg: make repo/server selection more modular

This gets rid of the ever-expanding conditional we had before and
replaces it with two case statements.

The first handles the command name. If it ends with 'pkg', we treat the
entire first part of the reponame, unless of course 'commitpkg' was
called directly. This allows one to add new symlinks such as
'gnome-unstablepkg'.

The second handles the server. Well-known repositories are listed and
passed to the appropriate server. All unusual repos are assumed to live
on gerolde and sent that direction.

Signed-off-by: Dan McGee <dan@archlinux.org>
Signed-off-by: Pierre Schmitz <pierre@archlinux.de>