diff -r ee9002b99595 -r f2c4224e6648 mercurial/upgrade_utils/engine.py
--- a/mercurial/upgrade_utils/engine.py	Thu Jan 14 16:34:58 2021 +0530
+++ b/mercurial/upgrade_utils/engine.py	Thu Jan 14 16:37:10 2021 +0530
@@ -449,7 +449,7 @@
         )
     )
 
-    if True:
+    if not upgrade_op.requirements_only:
         with dstrepo.transaction(b'upgrade') as tr:
             _clonerevlogs(
                 ui,
@@ -533,6 +533,7 @@
             # location. This is simpler.
             backupvfs.unlink(b'store/lock')
     else:
-        pass
+        ui.status(_(b'upgrading repository requirements\n'))
+        scmutil.writereporequirements(srcrepo, upgrade_op.new_requirements)
 
     return backuppath