Re: Performance degradation from long lines

[Phil Sainty]

The origin/scratch/so-long branch (adding so-long.el) is at a release
candidate stage, and I have rebased it over the current master branch.

Since the last discussions I've added a test suite, which is passing
on all the versions I've tested, being: 24.4 (the minimum supported
version), 24.5, 25.3, 26.1, 26.2, and current master, and I've dealt
to a variety of minor and backwards-compatibility issues in the process.

As previously discussed, the ELPA package (for Emacs 24,25,26) can be
built from this code.

https://git.savannah.nongnu.org/cgit/so-long.git/plain/so-long.el?h=wip
also has the same code, just with a different directory structure for
the test code).

There will be some continuing work to eliminate the use of advice in
Emacs 27 (e.g. via bug#35351), but I feel that the library is in a
good state, and could potentially be merged at this point.


-Phil