mercurial/changegroup.py

--- a/mercurial/changegroup.py	Sun Oct 06 23:36:51 2019 -0400
+++ b/mercurial/changegroup.py	Sun Oct 06 23:36:51 2019 -0400
@@ -1479,6 +1479,11 @@
         #
         # (or even to push subset of history)
         needv03 = True
+    if b'exp-sidedata-flag' in repo.requirements:
+        needv03 = True
+        # don't attempt to use 01/02 until we do sidedata cleaning
+        versions.discard(b'01')
+        versions.discard(b'02')
     if not needv03:
         versions.discard(b'03')
     return versions