- remove things which are clear from the context
- 0 is a valid descriptor number, hence "positive" → "non-negative"
- "positive" means greater than zero, hence "positive non-zero" → "positive"
- use oxford comma
- reword some things for clarity
sd_event_now() is a public function, so we must check all
arguments for validity. Update man page and add tests.
Sample debug message:
Assertion 'IN_SET(clock, CLOCK_REALTIME, CLOCK_REALTIME_ALARM, CLOCK_MONOTONIC, CLOCK_BOOTTIME, CLOCK_BOOTTIME_ALARM)' failed at src/libsystemd/sd-event/sd-event.c:2719, function sd_event_now(). Ignoring.
This completes the set of man pages for sd-event and contains some minor
other fixes for other man pages too.
The sd_event_set_name(3) man page is renamed to
sd_event_source_set_description(3), which is the correct name of the
concept today.
