Building postgresql with higher major version of separate libpq package

Hello all,

as to my recent findings, I'm not able to build postgresql 10.13
against libpq 12.1, as in that case, postgresql is missing changes
implemented in libpq 10.12 (and 12.2) [1]. So to rebase to postgresql
10.13 on a system with a separated libpq package shipped at version
12.1, I'm required to rebase the libpq package as well (even though
version 12.1 is technically higher than 10.13, it has been released
prior to 10.13, and is missing changes included in that version).

While I suppose that such compatibility is intended to be preserved
only for minor releases of separate major versions, I thought I'd
bring this up anyway, as it is something I haven't considered before.

[1] https://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=e60b480d39ee3401727a994988dd9117a3b48466

--
Patrik Novotný
Associate Software Engineer
Red Hat
panovotn(at)redhat(dot)com