Explicitly notify Codecov about upload completion (#85968)

This patch add an additional invocation of Codecov CLI that tells the
backend that we're done uploading. It is supposed to stop Codecov from
guessing whether to wait for more uploads for the CI or start
processing them already.

Upstream refs:
* https://docs.codecov.com/docs/cli-options#send-notifications
* https://docs.codecov.com/docs/notifications#preventing-notifications-until-youre-ready-to-send-notifications
* https://docs.codecov.com/docs/codecovyml-reference#codecovnotifymanual_trigger
* https://github.com/codecov/codecov-cli/pull/195 (d634ebd8f2)
* https://github.com/codecov/codecov-action/issues/1436
* https://github.com/codecov/engineering-team/issues/107
* https://github.com/codecov/roadmap/issues/20
* https://github.com/codecov/feedback/discussions/204#discussioncomment-8796433
* https://github.com/codecov/engineering-team/issues/1245
* https://github.com/codecov/engineering-team/issues/3
* https://github.com/codecov/worker/pull/14 (71626b6368)

.azure-pipelines/scripts/publish-codecov.py

@@ -118,16 +118,40 @@ def upload_files(codecov_bin: pathlib.Path, config_file: pathlib.Path, files: t.
         run(*cmd)
 
 
+def report_upload_completion(
+    codecov_bin: pathlib.Path,
+    config_file: pathlib.Path,
+    dry_run: bool = False,
+) -> None:
+    """Notify Codecov backend that all reports we wanted are in."""
+    cmd = [
+        codecov_bin,
+        '--disable-telem',
+        f'--codecov-yml-path={config_file}',
+        'send-notifications',
+    ]
+
+    if dry_run:
+        cmd.append('--dry-run')
+
+    run(*cmd)
+
+
 def main() -> None:
     args = parse_args()
 
     with tempfile.TemporaryDirectory(prefix='codecov-') as tmpdir:
         config_file = pathlib.Path(tmpdir) / 'config.yml'
-        config_file.write_text('')
+        # Refs:
+        # * https://docs.codecov.com/docs/codecovyml-reference#codecovnotifymanual_trigger
+        # * https://docs.codecov.com/docs/notifications#preventing-notifications-until-youre-ready-to-send-notifications
+        config_file.write_text('codecov:\n  notify:\n    manual_trigger: true')
 
         codecov_bin = install_codecov(pathlib.Path(tmpdir))
         files = process_files(args.path)
         upload_files(codecov_bin, config_file, files, args.dry_run)
+        # Ref: https://docs.codecov.com/docs/cli-options#send-notifications
+        report_upload_completion(codecov_bin, config_file, args.dry_run)
 
 
 if __name__ == '__main__':