git commit --allow-empty -m 'Dummy update'
mktag
mustfail 'not replacing previously-pushed version' +$push_spec1 +$push_spec2
+
+t-newtag
+re-prep
+mktag
+mustfail 'not replacing previously-pushed version' +$push_spec1 +$push_spec2
+
git reset --hard HEAD~
prep_dm_mangle () {