diff -r 49fd21f32695 -r 6266d19556ad mercurial/node.py
--- a/mercurial/node.py	Wed Mar 10 18:09:21 2021 +0100
+++ b/mercurial/node.py	Wed Jan 13 16:14:58 2021 +0100
@@ -21,29 +21,48 @@
         raise TypeError(e)
 
 
-nullrev = -1
-# In hex, this is '0000000000000000000000000000000000000000'
-nullid = b"\0" * 20
-nullhex = hex(nullid)
+def short(node):
+    return hex(node[:6])
+
 
-# Phony node value to stand-in for new files in some uses of
-# manifests.
-# In hex, this is '2121212121212121212121212121212121212121'
-newnodeid = b'!!!!!!!!!!!!!!!!!!!!'
-# In hex, this is '3030303030303030303030303030306164646564'
-addednodeid = b'000000000000000added'
-# In hex, this is '3030303030303030303030306d6f646966696564'
-modifiednodeid = b'000000000000modified'
+nullrev = -1
 
-wdirfilenodeids = {newnodeid, addednodeid, modifiednodeid}
-
-# pseudo identifiers for working directory
-# (they are experimental, so don't add too many dependencies on them)
+# pseudo identifier for working directory
+# (experimental, so don't add too many dependencies on it)
 wdirrev = 0x7FFFFFFF
-# In hex, this is 'ffffffffffffffffffffffffffffffffffffffff'
-wdirid = b"\xff" * 20
-wdirhex = hex(wdirid)
 
 
-def short(node):
-    return hex(node[:6])
+class sha1nodeconstants(object):
+    nodelen = 20
+
+    # In hex, this is '0000000000000000000000000000000000000000'
+    nullid = b"\0" * nodelen
+    nullhex = hex(nullid)
+
+    # Phony node value to stand-in for new files in some uses of
+    # manifests.
+    # In hex, this is '2121212121212121212121212121212121212121'
+    newnodeid = b'!!!!!!!!!!!!!!!!!!!!'
+    # In hex, this is '3030303030303030303030303030306164646564'
+    addednodeid = b'000000000000000added'
+    # In hex, this is '3030303030303030303030306d6f646966696564'
+    modifiednodeid = b'000000000000modified'
+
+    wdirfilenodeids = {newnodeid, addednodeid, modifiednodeid}
+
+    # pseudo identifier for working directory
+    # (experimental, so don't add too many dependencies on it)
+    # In hex, this is 'ffffffffffffffffffffffffffffffffffffffff'
+    wdirid = b"\xff" * nodelen
+    wdirhex = hex(wdirid)
+
+
+# legacy starting point for porting modules
+nullid = sha1nodeconstants.nullid
+nullhex = sha1nodeconstants.nullhex
+newnodeid = sha1nodeconstants.newnodeid
+addednodeid = sha1nodeconstants.addednodeid
+modifiednodeid = sha1nodeconstants.modifiednodeid
+wdirfilenodeids = sha1nodeconstants.wdirfilenodeids
+wdirid = sha1nodeconstants.wdirid
+wdirhex = sha1nodeconstants.wdirhex