maven
- https://cwiki.apache.org/confluence/display/MAVENOLD/Repository+Layout+-+Final
- https://cwiki.apache.org/confluence/display/MAVENOLD/Repository+Metadata apt
- https://wiki.debian.org/DebianRepository/Format
- http://www.ibiblio.org/gferg/ldp/giles/repository/repository-2.html goproxy
- https://github.com/elazarl/goproxy