diff -r a1e4fa9330d8 -r 421c9b3f2f4e mercurial/manifest.py
--- a/mercurial/manifest.py	Thu Aug 01 11:43:10 2024 -0400
+++ b/mercurial/manifest.py	Thu Aug 01 13:38:31 2024 +0100
@@ -493,6 +493,9 @@
 
     __bool__ = __nonzero__
 
+    def set(self, key, node, flags):
+        self._lm[key] = node, flags
+
     def __setitem__(self, key, node):
         self._lm[key] = node, self.flags(key)
 
@@ -1048,6 +1051,26 @@
                 del self._flags[f]
         self._dirty = True
 
+    def set(self, f, node, flags):
+        """Set both the node and the flags for path f."""
+        assert node is not None
+        if flags not in _manifestflags:
+            raise TypeError(b"Invalid manifest flag set.")
+        self._load()
+        dir, subpath = _splittopdir(f)
+        if dir:
+            self._loadlazy(dir)
+            if dir not in self._dirs:
+                self._dirs[dir] = treemanifest(
+                    self.nodeconstants, self._subpath(dir)
+                )
+            self._dirs[dir].set(subpath, node, flags)
+        else:
+            assert len(node) in (20, 32)
+            self._files[f] = node
+            self._flags[f] = flags
+        self._dirty = True
+
     def __setitem__(self, f, n):
         assert n is not None
         self._load()