Add Markdown support to package comments

Support Markdown syntax in package comments. Among other things, this
makes it easier to paste command line output and patches.
Signed-off-by: Lukas Fleischer <lfleischer@archlinux.org>

aurweb/scripts/rendercomment.py

@@ -2,6 +2,7 @@
 
 import sys
 import bleach
+import markdown
 
 import aurweb.db
 
@@ -22,9 +23,10 @@ def main():
 
     conn = aurweb.db.Connection()
 
-    html = get_comment(conn, commentid)
-    html = html.replace('\n', '<br>')
-    html = bleach.clean(html, tags=['br'])
+    text = get_comment(conn, commentid)
+    html = markdown.markdown(text, extensions=['nl2br'])
+    allowed_tags = bleach.sanitizer.ALLOWED_TAGS + ['p', 'br']
+    html = bleach.clean(html, tags=allowed_tags)
     save_rendered_comment(conn, commentid, html)
 
     conn.commit()

test/t2600-rendercomment.sh

@@ -11,7 +11,8 @@ test_expect_success 'Test comment rendering.' '
 	EOD
 	"$RENDERCOMMENT" 1 &&
 	cat <<-EOD >expected &&
-	Hello world!<br>This is a comment.
+	<p>Hello world!<br>
+	This is a comment.</p>
 	EOD
 	cat <<-EOD | sqlite3 aur.db >actual &&
 	SELECT RenderedComment FROM PackageComments WHERE ID = 1;