sched/clkinfo: reset `last` when activating an alarm

[bobrippling]

Oddly, my watch didn't go off this morning - I have a nightly backup which ran before the alarm time, so I had this snapshot of my alarm before it went off:

{
  "t": 23940000,
  "del": false,
  "on": true,
  "rp": false,
  "as": false,
  "dow": 127,
  "last": 23,
  "vibrate": "::",
  "msg": ""
}

I see two possible reasons the alarm didn't trigger:

• The scheduling code missed the window (unlikely, since this alarm has fired in the past)
• Somehow, alarm.last was already set to 23 (i.e. today), so the alarm was skipped. I can't see how it will have been set to 23, but it clearly was at the time of the snapshot.

This PR fixes the possible issue where a user has dismissed the alarm but then re-activates it via clkinfo. This shouldn't normally be possible for that alarm to retrigger in the same day (without time travel), but clearly somehow the .last property has been set on this alarm already.

[thyttan]

Thanks!

[thyttan]

I haven't tested this yet. But if you rebase on the changes Gordon made I can give it a try 👍

[bobrippling]

All sorted, and thanks - I would deploy to my gh-pages but I've got that in-use already I'm afraid! (#3626)

[bobrippling]

~All sorted, and thanks - I would deploy to my gh-pages but I've got that in-use already I'm afraid!~

Deployed!

[thyttan]

Sorry for not coming back sooner.

I just tried setting an alarm, then toggling it off then on again. It then fired at the set time a minute later.

Not an exhaustive test, but at least doesn't seem to break on my watch.

[bobrippling]

No worries, thanks for the check - I've been using this for a little while too with no issues. I could merge at the weekend if you've no objections?

[thyttan]

Yes I think that's fine 👍