This originally contained a change to fix src component detection. This was moved to a separate review now (D21579) to speed up review of the bugfix and allow a separate commit that could be MFCed.
While debugging the issue mentioned above, I added a showconfig command which I found useful enough to leave it in and document it in the man page.
Like discussed somewhere else, I also added an updatesready command that can be used to check if there are any pending fetched updates that can be installed. It exits on status code 2 in case there aren't any pending updates so that if one can tell apart exit 1 (=error) from it (right now there is no code path for that, but if more checks are added in the future this could be useful).
Finally, I changed the exit code of freebsd-update install in case there are no updates pending to be installed and there wasn't a fetch phase to 2 - this should allow future scripts to differentiate between "error" and "nothing to be done" without breaking existing jail managers like ezjail and iocell.
Besides documentation changed, I also added a comma in the manpage to pacify igor.
Happy to accept naming changes (like, if the reviewers happen to not like updatesready and showconfig). Feel free to correct my English.