Remove beforeunload listener for cancel button

app/assets/javascripts/blob_edit/blob_bundle.js

@@ -17,6 +17,11 @@ export default () => {
     const currentAction = $('.js-file-title').data('currentAction');
     const projectId = editBlobForm.data('project-id');
     const commitButton = $('.js-commit-button');
+    const cancelLink = $('.btn.btn-cancel');
+
+    cancelLink.on('click', () => {
+      window.onbeforeunload = null;
+    });
 
     commitButton.on('click', () => {
       window.onbeforeunload = null;

changelogs/unreleased/55344-only-prompt-user-once-when-navigating-away-from-file-editor.yml

+---
+title: Only prompt user once when navigating away from file editor
+merge_request: 23820
+author: Sam Bigelow
+type: fixed

spec/javascripts/blob_edit/blob_bundle_spec.js

@@ -14,6 +14,7 @@ describe('EditBlob', () => {
     setFixtures(`
       <div class="js-edit-blob-form">
         <button class="js-commit-button"></button>
+        <a class="btn btn-cancel" href="#"></a>
       </div>`);
     blobBundle();
   });
@@ -27,4 +28,10 @@ describe('EditBlob', () => {
 
     expect(window.onbeforeunload).toBeNull();
   });
+
+  it('removes beforeunload listener when cancel link is clicked', () => {
+    $('.btn.btn-cancel').click();
+
+    expect(window.onbeforeunload).toBeNull();
+  });
 });