In the "export-tar" action, fix the use of "--log-json" when exporting to stdout (#485).

borgmatic/borg/export_tar.py

@@ -41,7 +41,7 @@ def export_tar_archive(
         (local_path, 'export-tar')
         + (('--remote-path', remote_path) if remote_path else ())
         + (('--umask', str(umask)) if umask else ())
-        + ('--log-json',)
+        + (('--log-json',) if destination_path != '-' else ())
         + (('--lock-wait', str(lock_wait)) if lock_wait else ())
         + (('--info',) if logger.getEffectiveLevel() == logging.INFO else ())
         + (('--list',) if config.get('list_details') else ())

tests/unit/borg/test_export_tar.py

@@ -368,9 +368,7 @@ def test_export_tar_archive_calls_borg_with_stdout_destination_path():
     flexmock(module.flags).should_receive('make_repository_archive_flags').and_return(
         ('repo::archive',),
     )
-    insert_execute_command_mock(
-        ('borg', 'export-tar', '--log-json', 'repo::archive', '-'), capture=False
-    )
+    insert_execute_command_mock(('borg', 'export-tar', 'repo::archive', '-'), capture=False)
 
     module.export_tar_archive(
         dry_run=False,