histedit: cache description line Navigating the curses-based histedit interface can be pretty slow because it redraws everything whenever you make a change. This patch simply replaces `@property` by `@util.propertycache` on the `histeditrule.desc()` function so it's not re-calculated every time the screen needs to be re-rendered. I timed it on an example of 30 simple commits, where I moved the top commit down 25 steps and then up 25 steps after. Before this patch, that (the whole `hg histedit` invocation) took 11.6 s of CPU and after this patch it took 0.8 s). Differential Revision: https://phab.mercurial-scm.org/D9016

tests: make emacs test less strict It was failing like this for me: ``` @@ -2,7 +2,7 @@ $ emacs -q -no-site-file -batch -l $TESTDIR/../contrib/hg-test-mode.el \ > -f ert-run-tests-batch-and-exit Running 1 tests (*) (glob) - passed 1/1 hg-test-mode--compilation-mode-support + passed 1/1 hg-test-mode--compilation-mode-support (0.045732 sec) - Ran 1 tests, 1 results as expected (*) (glob) + Ran 1 tests, 1 results as expected, 0 unexpected (2020-09-11 16:49:56+0000, 0.046034 sec) ``` Differential Revision: https://phab.mercurial-scm.org/D9017