Early exit when no files are changed. (#456)

* Early exit when no files are changed.

As a consequence of the `checkAll` function call returning `true` if the length of `changedFiles` is 0, this must early-exit in order to avoid labeling empty PRs.

* Update dist.

* Update for new code styles.

* review changes requested

* Update dist.

* chore: prettify code

---------

Co-authored-by: MaksimZhukov <maksimzhukov@github.com>
Co-authored-by: IvanZosimov <ivanzosimov@github.com>

__tests__/main.test.ts

@@ -313,6 +313,15 @@ describe('run', () => {
     );
   });
 
+  it('does not add labels to PRs that have no changed files', async () => {
+    usingLabelerConfigYaml('only_pdfs.yml');
+    mockGitHubResponseChangedFiles();
+
+    await run();
+
+    expect(setLabelsMock).toHaveBeenCalledTimes(0);
+  });
+
   it('should use local configuration file if it exists', async () => {
     const configFile = 'only_pdfs.yml';
     const configFilePath = path.join(__dirname, 'fixtures', configFile);