system-upgrade: Refactor, allow any offline transaction

- Add the `dnf5 offline` command (not a plugin) with the same subcommands as the old `dnf4 system-upgrade`
- Make `dnf5 system-upgrade` a regular command, not a plugin, and have
  it share subcommands with `dnf5 offline` in addition to it
  implementing `system-upgrade download`
- Add `--offline` flag to `autoremove`, `distro-sync`, `downgrade`, `install`, `group
  install`, `group upgrade`, `reinstall`, `remove`, `swap`, and `upgrade` commands
- Change many references to "system upgrade" to "offline transaction"

For rpm-software-management#1052 and rpm-software-management#1224

dnf5-plugins/CMakeLists.txt

@@ -13,4 +13,3 @@ add_subdirectory("config-manager_plugin")
 add_subdirectory("copr_plugin")
 add_subdirectory("needs_restarting_plugin")
 add_subdirectory("repoclosure_plugin")
-add_subdirectory("system_upgrade_plugin")

dnf5.spec

@@ -62,6 +62,8 @@ Provides:       dnf5-command(advisory)
 Provides:       dnf5-command(clean)
 Provides:       dnf5-command(download)
 Provides:       dnf5-command(makecache)
+Provides:       dnf5-command(offline)
+Provides:       dnf5-command(system-upgrade)
 
 
 # ========== build options ==========
@@ -654,14 +656,13 @@ Provides:       dnf5-command(config-manager)
 Provides:       dnf5-command(copr)
 Provides:       dnf5-command(needs-restarting)
 Provides:       dnf5-command(repoclosure)
-Provides:       dnf5-command(system-upgrade)
 
 %description -n dnf5-plugins
 Core DNF5 plugins that enhance dnf5 with builddep, changelog,
 config-manager, copr, and repoclosure commands.
 
 %files -n dnf5-plugins -f dnf5-plugin-builddep.lang -f dnf5-plugin-changelog.lang -f dnf5-plugin-config-manager.lang -f dnf5-plugin-copr.lang -f dnf5-plugin-needs-restarting.lang -f dnf5-plugin-repoclosure.lang
-%config %{_unitdir}/dnf5-system-upgrade.service
+%config %{_unitdir}/dnf5-offline-transaction.service
 %{_libdir}/dnf5/plugins/*.so
 %{_mandir}/man8/dnf5-builddep.8.*
 %{_mandir}/man8/dnf5-copr.8.*

dnf5/CMakeLists.txt

@@ -2,6 +2,8 @@ if(NOT WITH_DNF5)
     return()
 endif()
 
+set(SYSTEMD_SYSTEM_UNIT_DIR /usr/lib/systemd/system)
+
 find_package(Threads)
 
 # set gettext domain for translations
@@ -32,7 +34,10 @@ target_link_libraries(dnf5 PRIVATE common libdnf5 libdnf5-cli Threads::Threads)
 install(TARGETS dnf5 RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR})
 
 pkg_check_modules(RPM REQUIRED rpm>=4.17.0)
-target_link_libraries(dnf5 PRIVATE ${RPM_LIBRARIES})
+pkg_check_modules(SDBUS_CPP REQUIRED sdbus-c++)
+pkg_check_modules(LIBSYSTEMD REQUIRED libsystemd)
+
+target_link_libraries(dnf5 PRIVATE ${RPM_LIBRARIES} ${SDBUS_CPP_LIBRARIES} ${LIBSYSTEMD_LIBRARIES})
 
 
 find_package(bash-completion)
@@ -47,7 +52,11 @@ 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 "${CMAKE_INSTALL_PREFIX}" PATTERN ".gitkeep" EXCLUDE)
 install(DIRECTORY "config/etc/" DESTINATION "${CMAKE_INSTALL_FULL_SYSCONFDIR}" PATTERN ".gitkeep" EXCLUDE)
-
+install(DIRECTORY "config/systemd/system/" DESTINATION "${SYSTEMD_SYSTEM_UNIT_DIR}" PATTERN ".gitkeep" EXCLUDE)
+install(CODE "execute_process(COMMAND ${CMAKE_COMMAND} -E create_symlink
+    ${SYSTEMD_SYSTEM_UNIT_DIR}/dnf5-offline-transaction.service
+    ${SYSTEMD_SYSTEM_UNIT_DIR}/system-update.target.wants/dnf5-offline-transaction.service)"
+)
 
 add_subdirectory(po)
 add_subdirectory("include")

dnf5/commands/autoremove/autoremove.cpp

@@ -19,6 +19,7 @@ along with libdnf.  If not, see <https://www.gnu.org/licenses/>.
 
 #include "autoremove.hpp"
 
+#include <dnf5/shared_options.hpp>
 #include <libdnf5/rpm/package_query.hpp>
 
 namespace dnf5 {
@@ -35,6 +36,7 @@ void AutoremoveCommand::set_parent_command() {
 void AutoremoveCommand::set_argument_parser() {
     get_argument_parser_command()->set_description(
         "Remove all unneeded packages originally installed as dependencies.");
+    create_offline_option(*this);
 }
 
 void AutoremoveCommand::configure() {

dnf5/commands/distro-sync/distro-sync.cpp

@@ -52,6 +52,7 @@ void DistroSyncCommand::set_argument_parser() {
     allow_erasing = std::make_unique<AllowErasingOption>(*this);
     auto skip_unavailable = std::make_unique<SkipUnavailableOption>(*this);
     auto skip_broken = std::make_unique<SkipBrokenOption>(*this);
+    create_offline_option(*this);
 }
 
 void DistroSyncCommand::configure() {

dnf5/commands/downgrade/downgrade.cpp

@@ -56,6 +56,7 @@ void DowngradeCommand::set_argument_parser() {
     auto skip_unavailable = std::make_unique<SkipUnavailableOption>(*this);
     auto skip_broken = std::make_unique<SkipBrokenOption>(*this);
     create_allow_downgrade_options(*this);
+    create_offline_option(*this);
 }
 
 void DowngradeCommand::configure() {

dnf5/commands/group/group_install.cpp

@@ -43,6 +43,7 @@ void GroupInstallCommand::set_argument_parser() {
     auto skip_broken = std::make_unique<SkipBrokenOption>(*this);
     create_allow_downgrade_options(*this);
     create_downloadonly_option(*this);
+    create_offline_option(*this);
 }
 
 void GroupInstallCommand::configure() {

dnf5/commands/group/group_upgrade.cpp

@@ -39,6 +39,7 @@ void GroupUpgradeCommand::set_argument_parser() {
 
     auto skip_unavailable = std::make_unique<SkipUnavailableOption>(*this);
     create_allow_downgrade_options(*this);
+    create_offline_option(*this);
 }
 
 void GroupUpgradeCommand::configure() {

dnf5/commands/install/install.cpp

@@ -67,6 +67,7 @@ void InstallCommand::set_argument_parser() {
     auto skip_unavailable = std::make_unique<SkipUnavailableOption>(*this);
     auto skip_broken = std::make_unique<SkipBrokenOption>(*this);
     create_allow_downgrade_options(*this);
+    create_offline_option(*this);
 }
 
 void InstallCommand::configure() {