progress: document progress.debug config option
I think it was not spotted by test-check-config.t that we had not
documented it because no caller refers to the ui object simply as "ui"
(it was either "self.ui" or just "self").
Differential Revision: https://phab.mercurial-scm.org/D5526
--- a/mercurial/help/config.txt Mon Jan 07 18:37:50 2019 -0500
+++ b/mercurial/help/config.txt Tue Jan 08 09:43:24 2019 -0800
@@ -1756,6 +1756,9 @@
possible. Some progress bars only offer indeterminate information, while others
have a definite end point.
+``debug``
+ Whether to print debug info when updating the progress bar. (default: False)
+
``delay``
Number of seconds (float) before showing the progress bar. (default: 3)