diff -r e9304c39e075 -r e2dfa403452d mercurial/debugcommands.py
--- a/mercurial/debugcommands.py	Wed Feb 14 08:14:46 2024 +0100
+++ b/mercurial/debugcommands.py	Fri Feb 23 04:26:03 2024 +0100
@@ -4077,6 +4077,30 @@
 
 
 @command(
+    b'debug::unbundle',
+    [
+        (
+            b'u',
+            b'update',
+            None,
+            _(b'update to new branch head if changesets were unbundled'),
+        )
+    ],
+    _(b'[-u] FILE...'),
+    helpcategory=command.CATEGORY_IMPORT_EXPORT,
+)
+def debugunbundle(ui, repo, *args, **kwargs):
+    """same as `hg unbundle`, but pretent to come from a push
+
+    This is useful to debug behavior and performance change in this case.
+    """
+    from . import commands  # avoid cycle
+
+    unbundle = cmdutil.findcmd(b'unbundle', commands.table)[1][0]
+    return unbundle(ui, repo, *args, _unbundle_source=b'push', **kwargs)
+
+
+@command(
     b'debugwalk', cmdutil.walkopts, _(b'[OPTION]... [FILE]...'), inferrepo=True
 )
 def debugwalk(ui, repo, *pats, **opts):