--- a/mercurial/debugcommands.py	Thu Jul 15 17:24:09 2021 +0200
+++ b/mercurial/debugcommands.py	Thu Jul 08 12:18:21 2021 +0200
@@ -7,6 +7,7 @@
 
 from __future__ import absolute_import
 
+import binascii
 import codecs
 import collections
 import contextlib
@@ -987,6 +988,24 @@
 
 
 @command(
+    b'debugdirstateignorepatternshash',
+    [],
+    _(b''),
+)
+def debugdirstateignorepatternshash(ui, repo, **opts):
+    """show the hash of ignore patterns stored in dirstate if v2,
+    or nothing for dirstate-v2
+    """
+    if repo.dirstate._use_dirstate_v2:
+        hash_offset = 16  # Four 32-bit integers before this field
+        hash_len = 20  # 160 bits for SHA-1
+        data_filename = repo.dirstate._map.docket.data_filename()
+        with repo.vfs(data_filename) as f:
+            hash_bytes = f.read(hash_offset + hash_len)[-hash_len:]
+        ui.write(binascii.hexlify(hash_bytes) + b'\n')
+
+
+@command(
     b'debugdiscovery',
     [
         (b'', b'old', None, _(b'use old-style discovery')),