无JIRA fix: 背景色不能遮住线,改为:after

src/less/base/tree/tree.expander.less

@@ -3,40 +3,34 @@
 
 .bi-tree-expander-popup.line {
 
-  &:before {
+  &:after {
     border-left: 1px dashed @border-color-dark-gray-line;
     position: absolute;
     content: "";
     height: 100%;
     left: -1px;
+    top: 0;
   }
 
-  &.solid:before {
+  &.solid:after {
     border-left: 1px solid @border-color-dark-gray-line;
-    position: absolute;
-    content: "";
-    height: 100%;
-    left: -1px;
   }
 }
 
 .bi-theme-dark {
   .bi-tree-expander-popup.line {
 
-    &:before {
+    &:after {
       border-left: 1px dashed @border-color-dark-gray-line-theme-dark;
       position: absolute;
       content: "";
       height: 100%;
       left: -1px;
+      top: 0;
     }
 
-    &.solid:before {
+    &.solid:after {
       border-left: 1px solid @border-color-dark-gray-line-theme-dark;
-      position: absolute;
-      content: "";
-      height: 100%;
-      left: -1px;
     }
   }
 }