add margin bottom for collapse button, add className option for level component

scm-ui-components/packages/ui-components/src/layout/Level.js

@@ -1,16 +1,18 @@
 //@flow
 import * as React from "react";
+import classNames from "classnames";
 
 type Props = {
+  className?: string,
   left?: React.Node,
   right?: React.Node
 };
 
 export default class Level extends React.Component<Props> {
   render() {
-    const { left, right } = this.props;
+    const { className, left, right } = this.props;
     return (
-      <div className="level">
+      <div className={classNames("level", className)}>
         <div className="level-left">{left}</div>
         <div className="level-right">{right}</div>
       </div>

scm-ui/src/repos/components/changesets/ChangesetDetails.js

@@ -35,6 +35,9 @@ const styles = {
   spacing: {
     marginRight: "1em"
   },
+  bottomMargin: {
+    marginBottom: "1rem !important"
+  },
   tags: {
     "& .tag": {
       marginLeft: ".25rem"
@@ -108,6 +111,7 @@ class ChangesetDetails extends React.Component<Props, State> {
         </div>
         <div>
           <Level
+            className={classes.bottomMargin}
             right={
               <Button
                 action={this.collapseDiffs}