> 1. seq 10 > /tmp/file
>
> 2. emacs -Q /tmp/file
>
> 3. (highlight-lines-matching-regexp "3")
>
>    This is bound to "M-s h l". I see the line containing "3" highlighted
>    in yellow, as expected
>
> 4. M-x auto-revert-mode
>
> 5. Back in the shell: seq 20 > /tmp/file
>
> auto-revert-mode kicks in, updating the buffer with the results of 'seq
> 20' (possibly updating to an empty buffer first, if we react immediately
> to the file truncation). At this point I would expect either:
>
> 1. The buffer being fully reverted, with all the highlighting
>    disappearing. This is what happens if we did M-x revert buffer
>
> 2. The buffer contents being reverted, but the highlighting being
>    reapplied
>
> In this auto-revert scenario, we get something in-between: after the
> auto-revert hi-lock-interactive-patterns still contains the highlighting
> regex, but no highlighting actually happens. It'd be really nice and
> useful if the highlighting stayed.

Now re-highlighting after revert is implemented in Emacs 30.

However, I noticed one problem that makes this feature unusable:
when a file contains file patterns, then after every revert it asks
again and again.  This is because hi-lock-file-patterns-policy
missed the value `always', now added in this patch: