> ps. some time ago deraadt@ suggested that perhaps previous output should
> be made available through some keyboard shortcut so one can scrub back
> and forth in the output history. iTerm2 calls this 'instant replay'
> https://iterm2.com/img/screenshots/instant_replay.gif - cool idea which
> might be a spiritual successor to the 'previous run as ghost output',
> but I don't have the cycles to work on that right now...

My idea was that watch shows you the live information.

But if you use the arrow keys to go left, it will show you previous
moments in time.

A very visible visual indicator would show you how far back you are
looking it, ie. the date you are looking at, and a time-delta of how
far back "5 minutes earlier" or "10 hours earlier".

If you choose right-arrow you can eventually end up back at current,
and once you hit current, it will advance.

When in the past you can also hit a different key to jump you to live-present,
maybe 'Home' or 'End' are suitable keys, maybe even both.

My idea is that I'm happy to see a live view but when things go weird
I'd like to see what the previous situations look like.

watch would need memory to support this.  It could be compressed somehow.
A correct data structure would not be accessed, and allow that memory to
swap out if not looked at, so the memory footprint is not very important.