Features:
+* new systemd-analyze "join" verb or so, for debugging services. Would be
+ nsenter on steroids, i.e invoke a shell or command line in an environment as
+ close as we can make it for the MainPID of a service. Should be built around
+ pidfd, so that we can reasonably robustly do this. Would only cover the
+ execution environment like namespaces, but not the privilege settings.
+
+* add a generic client to importd called importctl, then make machinectl just
+ chain-exec() it. Make sure importd/importctl can be used for sysext images,
+ portable images too.
+
* varlink: extend varlink IDL macros to include documentation strings
* Get rid of the symlinks in /run/systemd/units/* and exclusively use cgroupfs