From the help text:

  Commands that query the package database (list, latest, describe,
  field) operate on the list of databases specified by the flags
  --user, --global, and --package-conf.  If none of these flags are
  given, the default is --global --user.

This makes it possible to query just a single database (e.g. the
global one without the user one), which needed tricks to accomplish
before.