Compose metadata collections from directory trees

 AppStream is a metadata specification which permits software components to
 provide information about themselves to automated systems and end-users
 before the software is actually installed.
 This permits informative displays of new applications to users in software
 centers, as well as allowing a system to make decisions on which new software
 a user might want to install (e.g. missing firmware or media handlers).
 .
 This package extends the `appstreamcli` utility with a `compose` subcommand
 to generate AppStream metadata and media files from directory trees.