This saves us from spending 200-250ms of CPU time importing Django
again just to log that we're running a management command. On
`scripts/restart-server`, this saves us from one thundering herd of
Django startups when all the queue workers are restarted; but there's
still the Django startup for the `manage.py` process itself for each
worker, so on a machine with e.g. 2 (virtual) cores the restart is
still painful.
In this commit we basically do these things:
* Clear up section_head_offsets before pushing stuff in it so that
its size doesn't keep on growing indefinitely with time and users
opening emoji picker.
* Make use of popover element to find the correct element in DOM
to scan for section elements. This prevents us from filling stuff
twice into section_head_offsets because of presence of two
elements for '.emoji-popover-subheading' in DOM since popover
destroy is an async call.
* Using this popover element also helps in avoiding manuplation
of the DOM elements of the popover that was destroyed (Because
popover destroy is async it still maybe around). One instance of
this is associating scroll event with the right instance of
'.emoji-popover-emoji-map'.
In this we basically seed a single message for the user which will
be soft deactivated by sending a stream message / group PM to
ensure that is has at least one UserMessage row, since in real
world every human user will always have at least one User Message
row.
Normally the "n" key skips over muted streams, but if we
are currently narrowed inside a muted stream, it will now
go to the next topics within that stream.
For me the use case was that I have a stream I check up on
about once a day, and "n" would be super useful for me to
clear out unread counts while still skimming some content,
and without having to temporarily unmute the stream.
