How to fix RPM conflict on package installation in rpmbuild spec file

Which one to chose heavily depends what purpose or what script versions both packages contain. You probably don't want to get on the nerves of the other package maintainer, so discuss this.

In my situation, the "foo" package has been abandoned for a while. It's just still in the repositories for legacy reasons. The scripts in the "bar" package replace the outdated scripts, including /opt/scripts/myscript.pl. Therefore, in my situation, defining the "foo" package under "Obsoletes" in the bar.spec file is the way to go.

Updating bar.spec

As mentioned above, I updated bar.spec and added the Obsoletes definition:

ck@mint ~/Git/packages/bar $ cat bar.spec
Name:       bar
Version:    1.1.1
Release:    1%{dist}
Summary:    bar package contains handy scripts
Packager:   Claudio Kuenzler, <ck@claudiokuenzler.com>
Vendor:     Infiniroot GmbH

Group:      Application/System
License:    GPLv3
Source0:    %{name}-%{version}.tar.gz
BuildArch:  noarch

%if 0%{?rhel} == 6
Requires:    nc bind-utils perl
%endif
%if 0%{?rhel} == 7
Requires:    nmap-ncat bind-utils perl
%endif
%if 0%{?rhel} == 8
Requires:    nmap-ncat bind-utils perl
%endif
%if 0%{?rhel} == 9
Requires:    nmap-ncat bind-utils perl
%endif

Obsoletes:    foo

[...]

After building a new RPM package, it's time to test the new version.

RPM installation works, removes obsolete package

Now with a new bar package at hand, let's try the package installation/upgrade once more.

[root@rhel9 ~]# rpm -Uvh bar-1.1.1-1.el9.noarch.rpm
Verifying...                          ################################# [100%]
Preparing...                          ################################# [100%]
Updating / installing...
   1:bar-1.1.1-1.el9  ################################# [ 33%]
Cleaning up / removing...
   2:foo-3.5.0.1-1.el9 ################################# [ 67%]
   3:bar-1.0.99-1.el9  ################################# [100%]

The conflict is automatically resolved by removing the obsolete package "foo" and the package installation/upgrade of "bar" was successful.