bug#19796: 25.0.50; Regression: highlight-lines-matching-regexp can't re-highlight the same string

[Dima Kogan]

Hi.

The following commit broke some hi-lock functionality:

commit 6711a21f1125c0047c56eb266eb374c1ec90a967
Author: Stefan Monnier <monnier@iro.umontreal.ca>
Date:   Wed May 28 23:45:29 2014 -0400

    ...
    * lisp/hi-lock.el (hi-lock-mode, hi-lock-unface-buffer)
    (hi-lock-set-pattern, hi-lock-set-file-patterns): Use font-lock-flush.
    ...


Recipe to reproduce:

1. seq 1000 > /tmp/dat
2. emacs -Q /tmp/dat
3. M-s h l 7       (highlight all lines matching "7")
4. M-s h u [enter] (un-highlight the default, "7" in this case)
5. M-s h l 7       (highlight all lines matching "7" again)

After that commit, nothing is highlighted anymore