The --external-cache-only option is useful for client-side
use cases where writing cache files inside the repository itself
may interfere with repository verification. This option is
currently supported for --update and --update-pkg-desc-index
actions, for which consumers of the corresponding
It's necessary to use urlquote for correct behavior with ftp, http,
and https, since it's possible for file names to contain percent
encoded characters that need to be protected by an additional layer
of percent encoding. For other protocols such as sftp and rsync,
all characters are interpreted
