libxbps:
 - transaction: avoid fetching the whole pkg when updating and only fetch
   modified files from target pkg.
 - transaction: check for free space in all affected top-level dirs.
 - transaction: check all pkg top-level dirs to see if they are writable.
 - cache: download cached packages and signatures into a per repository
   directory like repodata files in /var/db/xbps

xbps-*:
 - Document exit codes.

xbps-create:
 - Move all configuration files to <prefix>/share/<pkgname>/conf/<cffile>.
 - Add -i --installed option to create binpkg from an installed version.

xbps-fetch:
 - stdout support
 - configurable libfetch timeout
 - configurable number of connection retries

xbps-digest:
 - blake2b support

Issues listed at https://github.com/void-linux/xbps/issues