Add a way to more conveniently log/debug nnmail splitting

* doc/misc/gnus.texi (Fancy Mail Splitting): Mention it.

* lisp/gnus/nnmail.el (nnmail-debug-splitting): New variable.

* lisp/gnus/nnmail.el (nnmail-log-split): New function.
(nnmail-split-it): Use it.

1 files changed, 3 insertions, 0 deletions

diff --git a/doc/misc/gnus.texi b/doc/misc/gnus.texi
index 5e41ff2e4c8..7c5bc3eee85 100644
--- a/doc/misc/gnus.texi
+++ b/doc/misc/gnus.texi
@@ -15594,6 +15594,9 @@ outgoing messages are written to an ``outgoing'' group, you could set
 Otherwise, answers to all your messages would end up in the
 ``outgoing'' group.
 
+If @code{nnmail-debug-splitting} is non-@code{nil}, the mail splitting
+code will log all splitting decisions to the @samp{*nnmail split*} buffer.
+
 
 @node Group Mail Splitting
 @subsection Group Mail Splitting