target: implicitly shutdown targets on shutdown, so that they are pulled into the final transaction and may be used for synchronization

src/target.c

@@ -75,7 +75,8 @@ static int target_add_default_dependencies(Target *t) {
                         if ((r = unit_add_dependency(UNIT(t), UNIT_AFTER, other, true)) < 0)
                                 return r;
 
-        return 0;
+        /* Make sure targets are unloaded on shutdown */
+        return unit_add_dependency_by_name(UNIT(t), UNIT_CONFLICTED_BY, SPECIAL_SHUTDOWN_TARGET, NULL, true);
 }
 
 static int target_add_getty_dependencies(Target *t) {

units/halt.target

@@ -9,6 +9,7 @@
 
 [Unit]
 Description=Halt
+DefaultDependencies=no
 Requires=halt.service
 After=halt.service
 AllowIsolate=yes

units/poweroff.target

@@ -9,6 +9,7 @@
 
 [Unit]
 Description=Power-Off
+DefaultDependencies=no
 Names=runlevel0.target
 Requires=poweroff.service
 After=poweroff.service

units/reboot.target

@@ -9,6 +9,7 @@
 
 [Unit]
 Description=Reboot
+DefaultDependencies=no
 Names=runlevel6.target
 Requires=reboot.service
 After=reboot.service

units/shutdown.target

@@ -9,5 +9,6 @@
 
 [Unit]
 Description=Shutdown
+DefaultDependencies=no
 RefuseManualStart=yes
 IgnoreDependencyFailure=yes