Comment # 1 on bug 956989 from Boris Manojlovic

I have updated package with and fixed %pretrans scriptlet
What is now done is separation of handling rpm issue (dir to symlink) and
handling
of old package configuration but from %pre where it belongs
https://build.opensuse.org/package/show/home:bmanojlovic/squid-3-5-10.server_proxy

I have tested this behavior with update from 3.5 to 4 (irrelevant) with
replacing symlinks with dirs and it has performed rename and update correctly
afterward