What is the best project management package?

APT relies on the concept of "repositories" in order to find software and resolve dependencies. A repository is a directory containing packages along with an index file. The Debian project keeps a central repository of over 17,000 software packages ready for download and installation. For extra packages, any number of additional repositories can be added to APT's sources.list configuration file and then be queried by APT. Problems may appear when several sources offer the same package(s). Systems that have such possibly conflicting sources can use APT pinning to control which sources should be preferred. Once a package repository has been specified (like during the system installation), packages in that repository can be installed without specifying a source.