The -contrib port depends on the -client, and the version of this dependency is hardcoded in the Makefile.
When the Makefile was copied for version 13, this was not changed, so the postgresql13-contrib package has a dependency on postgresql12-client.
Proposed fix: Replace the fixed version with the same expression that is in the -server Makefile.
A commit references this bug:
Date: Fri Sep 25 15:53:44 UTC 2020
New revision: 550051
Fix depenedency for postgresql13-contrib
And avoid hardcoding the version for all other versions as well, per suggestion
in the PR.
Submitted by: Christian Ullrich
*** Bug 249911 has been marked as a duplicate of this bug. ***