message: Make `copy-file` feature work on gists
diff: @@ -3,9 +3,10 @@ import select from 'select-dom';
  import delegate from 'delegate-it';
  import copyToClipboard from 'copy-text-to-clipboard';
  import features from '../libs/features';
  +import {groupSiblings} from '../libs/group-buttons';
  function handleClick({currentTarget: button}: React.MouseEvent<HTMLButtonElement>): void {
  - const file = button.closest('.Box');
  + const file = button.closest('.Box, .js-gist-file-update-container');
  const content = select.all('.blob-code-inner', file!)
  .map(({innerText: line}) => line === '\n' ? '' : line) // Must be `.innerText`
  .join('\n');
  @@ -13,8 +14,8 @@ function handleClick({currentTarget: button}: React.MouseEvent<HTMLButtonElement
  }
  function renderButton(): void {
  - for (const blameButton of select.all('[data-hotkey="b"]')) {
  - blameButton
  + for (const button of select.all('.file-actions .btn, [data-hotkey="b"]')) {
  + button
  .parentElement! // `BtnGroup`
  .prepend(
  <button
  @@ -25,6 +26,7 @@ function renderButton(): void {
  Copy
  </button>
  );
  + groupSiblings(button);
  }
  }
  