issue2551094 - simplemde now handles linebreaks like markdown backends

Single newlines in simplemde editor were not being displayed with hard
linebreaks. Original patch changed Markdown and Markdown2 backends to
implement non-standard hard linebreak on embedded newline. Mistune
does not support that without having to write a new plugin.

Rather than changing the backends, change the simplemde frontend call
to not support github flavored markdown support where newline is the
same as having two trailing spaces followed by a newline (markdown
standard for embedding a linebreak).

Author: rouilj

CHANGES.txt

@@ -36,6 +36,9 @@ Fixed:
   cheeseshop.  (John Rouillard)
 - issue2551093 - return plain text if markdown formatter throws exception
   (reported by Cedric Krier, fix by John Rouillard)
+- issue2551094 - make simplemde handle line breaks the same as the
+  backend markdown formmatters. (report: Cedric Krier, patch: Christof
+  Meerwald) 
 
 Features:
 - issue2550522 - Add 'filter' command to command-line

share/roundup/templates/jinja2/html/issue.item.html

@@ -32,7 +32,7 @@
       var node = $('#change_note')[0];
       var initSimpleMde = function () {
         node.parentNode.appendChild($('<input/>', { type: 'hidden', name: 'msg-1@type', value: 'text/markdown'})[0]);
-        var simplemde = new SimpleMDE({ element: node, status: false, styleSelectedText: false });
+        var simplemde = new SimpleMDE({ element: node, status: false, styleSelectedText: false, renderingConfig: {singleLineBreaks: false}});
         simplemde.render();
       };
       {% if context.id %}