Fixed misplaced mirror button

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/19191

app/assets/stylesheets/pages/projects.scss

@@ -640,3 +640,19 @@ pre.light-well {
     width: 300px;
   }
 }
+
+.project-mirror-text {
+  @media (min-width: $screen-sm-min) {
+    float: left;
+    line-height: 35px;
+  }
+}
+
+.project-mirror-button {
+  margin-top: 10px;
+
+  @media (min-width: $screen-sm-min) {
+    float: right;
+    margin-top: 0;
+  }
+}

app/views/projects/commits/_mirror_status.html.haml

 - if @project.mirror?
-  .gray-content-block.second-block
-    .pull-right
-      = render "shared/mirror_update_button"
-
+  .prepend-top-default.gray-content-block.second-block.clearfix
     - import_url = @project.safe_import_url
-    .oneline
+    .oneline.project-mirror-text
       This project is mirrored from #{link_to import_url, import_url}.
 
       = render "shared/mirror_status"
@@ -13,3 +10,5 @@
         %span.has-tooltip{data: { html: "true", title: branch_diverged_tooltip_message }}
           = icon('exclamation-triangle')
           This branch has diverged from upstream.
+    .project-mirror-button
+      = render "shared/mirror_update_button"