+* the default stop timeout for units is not documented anywhere.
+
+* .timer units should optionally support CLOCK_BOOTTIME in addition to CLOCK_MONOTONIC
+
+* rm_rf() should be able to remove subvolumes
+
+* systemd-run should support a mode where we wait for the unit to be started up
+
+* create a btrfs qgroup for /var/lib/machines, and add all container
+ subvolumes we create to it.
+
+* nspawn: add --overlay= to support overlay file systems, similar to
+ --tmpfs= and --bind=.
+
+* When logging about multiple units (stopping BoundTo units, conflicts, etc.),
+ log both units as UNIT=, so that journalctl -u triggers on both.
+