Fix Microsoft/vscode-pull-request-github#893. Avoid margin collapse

src/vs/workbench/parts/comments/electron-browser/commentThreadWidget.ts

@@ -622,8 +622,9 @@ export class ReviewZoneWidget extends ZoneWidget {
 			const lineHeight = this.editor.getConfiguration().lineHeight;
 			const arrowHeight = Math.round(lineHeight / 3);
 			const frameThickness = Math.round(lineHeight / 9) * 2;
+			console.log(dimensions);
 
-			const computedLinesNumber = Math.ceil((headHeight + dimensions.height + arrowHeight + frameThickness) / lineHeight);
+			const computedLinesNumber = Math.ceil((headHeight + dimensions.height + arrowHeight + frameThickness + 8 /** margin bottom to avoid margin collapse */) / lineHeight);
 			this._relayout(computedLinesNumber);
 		}
 	}

src/vs/workbench/parts/comments/electron-browser/media/review.css

@@ -34,6 +34,10 @@
 	display: none !important;
 }
 
+.monaco-editor .review-widget .body {
+	overflow: hidden;
+}
+
 .monaco-editor .review-widget .body .review-comment {
 	padding: 8px 16px 8px 20px;
 	display: flex;
@@ -198,8 +202,7 @@
 }
 
 .monaco-editor .review-widget .body .comment-form {
-	margin: 0 20px;
-	padding: 8px 0;
+	margin: 8px 20px;
 }
 
 .monaco-editor .review-widget .validation-error {