Add timestamp to .bak

Author: WardBrian

cmdstanpy/model.py

@@ -9,6 +9,7 @@
 import sys
 from collections import OrderedDict
 from concurrent.futures import ThreadPoolExecutor
+from datetime import datetime
 from io import StringIO
 from multiprocessing import cpu_count
 from pathlib import Path
@@ -376,7 +377,12 @@ def format(
             if overwrite_file:
                 if result:
                     if backup:
-                        shutil.copyfile(self.stan_file, self.stan_file + '.bak')
+                        shutil.copyfile(
+                            self.stan_file,
+                            self.stan_file
+                            + '.bak-'
+                            + datetime.now().strftime("%Y%m%d%H%M%S"),
+                        )
                     with (open(self.stan_file, 'w')) as file_handle:
                         file_handle.write(result)
             else:

test/data/.gitignore

@@ -6,5 +6,6 @@
 # and we re-ignore hpp and exe files
 *.hpp
 *.exe
-*.*bak
+*.testbak
+*.bak-*
 !return_one.hpp

test/test_model.py

@@ -7,6 +7,7 @@
 import shutil
 import tempfile
 import unittest
+from glob import glob
 from test import CustomTestCase
 from unittest.mock import MagicMock, patch
 
@@ -409,7 +410,7 @@ def test_model_format_deprecations(self):
         shutil.copy(stan, stan + '.testbak')
         try:
             model.format(overwrite_file=True, canonicalize=True)
-            self.assertTrue(os.path.exists(stan + '.bak'))
+            self.assertEqual(len(glob(stan + '.bak-*')), 1)
         finally:
             shutil.copy(stan + '.testbak', stan)