Base: Add support for repository configuration in /usr

This enables shipping packaged repositories and variables in /usr,
freeing up /etc for exclusively user-added repository configuration.

dnf5.spec

@@ -305,6 +305,8 @@ Package management library.
 %dir %{_datadir}/dnf5/repos.override.d
 %dir %{_sysconfdir}/dnf/repos.override.d
 %dir %{_sysconfdir}/dnf/libdnf5-plugins
+%dir %{_datadir}/dnf5/repos.d
+%dir %{_datadir}/dnf5/vars.d
 %dir %{_libdir}/libdnf5
 %{_libdir}/libdnf5.so.1*
 %license lgpl-2.1.txt

dnf5/CMakeLists.txt

@@ -42,7 +42,7 @@ endif()
 
 install(FILES bash-completion/dnf5 DESTINATION ${BASH_COMPLETION_COMPLETIONSDIR})
 install(FILES "README.plugins" DESTINATION "${CMAKE_INSTALL_FULL_LIBDIR}/dnf5/plugins" RENAME "README")
-install(DIRECTORY "config/usr/" DESTINATION "${CMAKE_INSTALL_PREFIX}")
+install(DIRECTORY "config/usr/" DESTINATION "${CMAKE_INSTALL_PREFIX}" PATTERN ".gitkeep" EXCLUDE)
 install(DIRECTORY "config/etc/" DESTINATION "${CMAKE_INSTALL_FULL_SYSCONFDIR}" PATTERN ".gitkeep" EXCLUDE)
 
 

include/libdnf5/conf/const.hpp

@@ -36,11 +36,12 @@ constexpr const char * CONF_DIRECTORY = "/etc/dnf/libdnf5.conf.d";
 
 constexpr const char * PLUGINS_CONF_DIR = "/etc/dnf/libdnf5-plugins";
 
-const std::vector<std::string> REPOSITORY_CONF_DIRS{"/etc/yum.repos.d", "/etc/distro.repos.d"};
+const std::vector<std::string> REPOSITORY_CONF_DIRS{
+ "/etc/yum.repos.d", "/etc/distro.repos.d", "/usr/share/dnf5/repos.d"};
 constexpr const char * REPOS_OVERRIDE_DIR = "/etc/dnf/repos.override.d";
 
 // More important varsdirs must be on the end of vector
-const std::vector<std::string> VARS_DIRS{"/etc/dnf/vars"};
+const std::vector<std::string> VARS_DIRS{"/usr/share/dnf5/vars.d", "/etc/dnf/vars"};
 
 const std::vector<std::string> GROUP_PACKAGE_TYPES{"mandatory", "default", "conditional"};
 const std::vector<std::string> INSTALLONLYPKGS{