nano.spec: Introduce default-editor package

The package is needed for the smooth upgrade process if you don't have
nano as a default editor.

Currently 'dnf upgrade' to newer Fedoras ends with error because
'nano-default-editor' is in DNF group 'Standard', which DNF wants to
install/upgrade during upgrade process. This ends in conflict between
'nano-default-editor' and any other 'system-default-editor' providers,
such as 'vim-default-editor' and manuall intervention is needed.

To fix the behavior we introduce 'default-editor' subpackage, which will
have a weak dependency on 'nano-default-editor', so fresh installations
will have 'nano' as default, and non-nano users will have an upgrade
process without this error.

Requiring system-default-editor was added based on pkratoch's review.
Now default-editor is removed if nano-default-editor is removed and if
nano-default-editor is excluded from a DNF transaction which installs
default-editor, DNF will satisfy the dependency with another package
which provides system-default-editor.

nano.spec

@@ -8,7 +8,7 @@
 Summary:         A small text editor
 Name:            nano
 Version:         5.8
-Release:         1%{?dist}
+Release:         2%{?dist}
 License:         GPLv3+
 URL:             https://www.nano-editor.org
 Source:          https://www.nano-editor.org/dist/latest/%{name}-%{version}.tar.xz
@@ -45,6 +45,17 @@ BuildArch:       noarch
 %description default-editor
 This package ensures the EDITOR shell variable
 is set in common shells to GNU nano.
+
+%package -n default-editor
+Summary:         Metapackage for DNF group
+Recommends:      nano-default-editor
+Requires:        system-default-editor
+BuildArch:       noarch
+
+%description -n default-editor
+The package acts as a placeholder in DNF group 'Standard', which will
+install nano-default-editor on fresh installs and it will not block users
+who don't have nano as a default editor during upgrade.
 %endif
 
 %prep
@@ -105,10 +116,15 @@ install -Dpm 0644 %{SOURCE13} %{buildroot}%{_datadir}/fish/vendor_conf.d/%{basen
 %config(noreplace) %{_sysconfdir}/profile.d/nano-default-editor.*
 %dir %{_datadir}/fish/vendor_conf.d
 %{_datadir}/fish/vendor_conf.d/nano-default-editor.fish
+
+%files -n default-editor
 %endif
 
 
 %changelog
+* Wed Jun 16 2021 Zdenek Dohnal <zdohnal@redhat.com> - 5.8-2
+- introduce 'default-editor' subpackage to support smooth non-nano upgrades (#1955884)
+
 * Tue Jun 15 2021 Kamil Dudka <kdudka@redhat.com> - 5.8-1
 - new upstream release