Add a basic depot_tools version information

depot_tools has no versioning. It's hard to know if reported issues were
caused due to outdated depot_tools or actual unresolved bug.

This CL adds basic information about depot_tools version and it's
included in presubmit failure.

R=aravindvasudev@google.com, gavinmak@google.com

Change-Id: If8577c0826063693a7278a57a0cce629d4b1325f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3541061
Reviewed-by: Aravind Vasudevan <aravindvasudev@google.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>
diff --git a/utils.py b/utils.py
new file mode 100644
index 0000000..3f16ce9
--- /dev/null
+++ b/utils.py
@@ -0,0 +1,25 @@
+# Copyright 2022 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import os
+import subprocess
+
+
+def depot_tools_version():
+  depot_tools_root = os.path.dirname(os.path.abspath(__file__))
+  try:
+    commit_hash = subprocess.check_output(['git', 'rev-parse', 'HEAD'],
+                                          cwd=depot_tools_root).decode(
+                                              'utf-8', 'ignore')
+    return 'git-%s' % commit_hash
+  except Exception:
+    pass
+
+  # git check failed, let's check last modification of frequently checked file
+  try:
+    mtime = os.path.getmtime(
+        os.path.join(depot_tools_root, 'infra', 'config', 'recipes.cfg'))
+    return 'recipes.cfg-%d' % (mtime)
+  except Exception:
+    return 'unknown'