feat(git-node): prompt before attempting branch-diff (#869)

Author: aduh95

lib/prepare_release.js

@@ -167,7 +167,11 @@ export default class ReleasePreparation extends Session {
       return this.prepareSecurity();
     }
 
-    if (this.runBranchDiff) {
+    const runBranchDiff = await cli.prompt(
+      'Do you want to check if any additional commits could be backported ' +
+      '(recommended except for Maintenance releases)?',
+      { defaultAnswer: this.runBranchDiff });
+    if (runBranchDiff) {
       // TODO: UPDATE re-use
       // Check the branch diff to determine if the releaser
       // wants to backport any more commits before proceeding.