--- a/mercurial/revlogutils/docket.py	Mon May 03 12:34:41 2021 +0200
+++ b/mercurial/revlogutils/docket.py	Mon May 03 12:34:52 2021 +0200
@@ -28,36 +28,55 @@
 # * 4 bytes: revlog version
 #          |   This is mandatory as docket must be compatible with the previous
 #          |   revlog index header.
-S_HEADER = struct.Struct(constants.INDEX_HEADER.format)
+# * 8 bytes: size of index data
+S_HEADER = struct.Struct(constants.INDEX_HEADER.format + 'L')
 
 
 class RevlogDocket(object):
     """metadata associated with revlog"""
 
-    def __init__(self, revlog, version_header=None):
+    def __init__(self, revlog, version_header=None, index_end=0):
         self._version_header = version_header
         self._dirty = False
         self._radix = revlog.radix
         self._path = revlog._docket_file
         self._opener = revlog.opener
+        self._index_end = index_end
 
     def index_filepath(self):
         """file path to the current index file associated to this docket"""
         # very simplistic version at first
         return b"%s.idx" % self._radix
 
-    def write(self, transaction):
+    @property
+    def index_end(self):
+        return self._index_end
+
+    @index_end.setter
+    def index_end(self, new_size):
+        if new_size != self._index_end:
+            self._index_end = new_size
+            self._dirty = True
+
+    def write(self, transaction, stripping=False):
         """write the modification of disk if any
 
         This make the new content visible to all process"""
         if self._dirty:
-            transaction.addbackup(self._path, location=b'store')
+            if not stripping:
+                # XXX we could, leverage the docket while stripping. However it
+                # is not powerfull enough at the time of this comment
+                transaction.addbackup(self._path, location=b'store')
             with self._opener(self._path, mode=b'w', atomictemp=True) as f:
                 f.write(self._serialize())
             self._dirty = False
 
     def _serialize(self):
-        return S_HEADER.pack(self._version_header)
+        data = (
+            self._version_header,
+            self._index_end,
+        )
+        return S_HEADER.pack(*data)
 
 
 def default_docket(revlog, version_header):
@@ -72,9 +91,10 @@
 def parse_docket(revlog, data):
     """given some docket data return a docket object for the given revlog"""
     header = S_HEADER.unpack(data[: S_HEADER.size])
-    (version_header,) = header
+    version_header, index_size = header
     docket = RevlogDocket(
         revlog,
         version_header=version_header,
+        index_end=index_size,
     )
     return docket