Don't treat asterisks in list items as italic in Markdown

Fixes an issue where asterisks used for list items were converted to
underscores.

Author: rspeicher

lib/slack/messages/formatting.rb

@@ -75,7 +75,7 @@ def url_link(text, url)
         #
         def markdown(text)
           text
-            .gsub(/(?<!\*)\*([^*]+)\*(?!\*)/, '_\1_') # italic
+            .gsub(/(?<!\*)\*([^*\n]+)\*(?!\*)/, '_\1_') # italic
             .gsub(/\*\*\*(.*?)\*\*\*/, '*_\1_*') # bold & italic
             .gsub(/\*\*(.*?)\*\*/, '*\1*') # bold
             .gsub(/~~(.*?)~~/, '~\1~') # strikethrough

spec/slack/messages/formatting_spec.rb

@@ -149,6 +149,18 @@
       )
     end
 
+    it "doesn't treat list items as text formatting" do
+      msg = <<~MSG
+        Une liste:
+
+        * Article 1
+        * Article 2
+        * Article 3
+      MSG
+
+      expect(formatting.markdown(msg)).to eq msg
+    end
+
     it "doesn't format other markdown" do
       expect(formatting.markdown('## A heading\n_Italics_\n`code`')).to eq '## A heading\n_Italics_\n`code`'
     end