This isn't a real subcommand like the others. The option processing
just intercepts it and prints the output. Given that we're subcommand
based, it makes sense to support this in addition to --help.
(cherry picked from commit 3743d6d208)
(cherry picked from commit 3c6478e179)
This adds the sources command which can be used to list, add, change,
and delete sources using the TOML formatted source file.
(cherry picked from commit 6f6ce410c0)
