Improve mr compare message when base is different

app/assets/stylesheets/pages/merge_requests.scss

@@ -402,12 +402,11 @@
   }
 
   .content-block {
+    border-top: 1px solid $border-color;
     padding: $gl-padding-top $gl-padding;
   }
 
   .comments-disabled-notif {
-    border-top: 1px solid $border-color;
-
     .btn {
       margin-left: 5px;
     }

app/helpers/merge_requests_helper.rb

@@ -123,4 +123,8 @@ module MergeRequestsHelper
   def version_index(merge_request_diff)
     @merge_request_diffs.size - @merge_request_diffs.index(merge_request_diff)
   end
+
+  def different_base?(version1, version2)
+    version1 && version2 && version1.base_commit_sha != version2.base_commit_sha
+  end
 end

app/views/projects/merge_requests/show/_versions.html.haml

@@ -64,13 +64,16 @@
                       #{@merge_request.target_branch} (base)
                     .monospace #{short_sha(@merge_request_diff.base_commit_sha)}
 
-    - if @start_version && @start_version.base_commit_sha != @merge_request_diff.base_commit_sha
+    - if different_base?(@start_version, @merge_request_diff)
       .content-block
+        = icon('info-circle')
         Selected versions have different base commits.
         Changes will include
         = link_to namespace_project_compare_path(@project.namespace, @project, from: @start_version.base_commit_sha, to: @merge_request_diff.base_commit_sha) do
           new commits
-        from #{@merge_request.target_branch}
+        from
+        %code #{@merge_request.target_branch}
+
     - unless @merge_request_diff.latest? && !@start_sha
       .comments-disabled-notif.content-block
         = icon('info-circle')