Merge pull request #9079 from liuyl/buttongroups

Fix #7108: btn group styling

dist/css/bootstrap.css

@@ -3257,12 +3257,12 @@ button.close {
   border-radius: 0;
 }
 
-.btn-group-vertical .btn:first-child {
+.btn-group-vertical .btn:first-child:not(:last-child) {
   border-bottom-right-radius: 0;
   border-bottom-left-radius: 0;
 }
 
-.btn-group-vertical .btn:last-child {
+.btn-group-vertical .btn:last-child:not(:first-child) {
   border-top-right-radius: 0;
   border-top-left-radius: 0;
 }

less/button-groups.less

@@ -142,10 +142,10 @@
   &:not(:first-child):not(:last-child) {
     border-radius: 0;
   }
-  &:first-child {
+  &:first-child:not(:last-child) {
     .border-bottom-radius(0);
   }
-  &:last-child {
+  &:last-child:not(:first-child) {
     .border-top-radius(0);
   }
 }