Use project_users_select_tag for Issue form and MR form

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

app/assets/stylesheets/generic/forms.scss

@@ -51,3 +51,27 @@ label {
 .input-mn-300 {
   min-width: 300px;
 }
+
+.custom-form-control {
+  width: 150px;
+}
+
+@media (min-width: $screen-sm-min) {
+  .custom-form-control {
+    width: 150px;
+  }
+}
+
+/* Medium devices (desktops, 992px and up) */
+@media (min-width: $screen-md-min) {
+  .custom-form-control {
+    width: 170px;
+  }
+}
+
+/* Large devices (large desktops, 1200px and up) */
+@media (min-width: $screen-lg-min) {
+  .custom-form-control {
+    width: 200px;
+  }
+}

app/assets/stylesheets/generic/selects.scss

 /** Select2 selectbox style override **/
-
 .select2-container, .select2-container.select2-drop-above {
   .select2-choice {
     background: #FFF;
@@ -12,9 +11,13 @@
 }
 
 .select2-drop-active {
-  border: 1px solid #BBB;
+  border: 1px solid #BBB !important;
   margin-top: 4px;
 
+  &.select2-drop-above {
+    margin-bottom: 8px;
+  }
+
   .select2-search input {
     background: #fafafa;
     border-color: #DDD;

app/views/projects/issues/_form.html.haml

@@ -24,7 +24,7 @@
           %i.icon-user
           Assign to
         .col-sm-10
-          = f.select(:assignee_id, assignee_options(@issue), { include_blank: "Select a user" }, {class: 'select2'})
+          = project_users_select_tag('issue[assignee_id]', placeholder: 'Select a user', class: 'custom-form-control')
            
           = link_to 'Assign to me', '#', class: 'btn btn-small assign-to-me-link'
     .form-group

app/views/projects/merge_requests/_form.html.haml

@@ -47,7 +47,7 @@
           %i.icon-user
           Assign to
         .col-sm-10
-          = f.select(:assignee_id, assignee_options(@merge_request), { include_blank: "Select a user" }, {class: 'select2'})
+          = project_users_select_tag('merge_request[assignee_id]', placeholder: 'Select a user', class: 'custom-form-control')
            
           = link_to 'Assign to me', '#', class: 'btn btn-small assign-to-me-link'
     .form-group