git rebase does not support a --recurse-submodules switch to automatically
check out the submodules at their registered commits during or after a rebase.
Instead, let's use the post-rewrite git hook to do this ourselves.
We are saying in public that the protocl is stable and can be easily
reimplemented, so provide an example doing so in the documentation,
license as MIT-0 so that it can be copied and pasted at will.
This also drop the support of /run/systemd/netif/persistent-storage-ready,
as the file is anyway removed when networkd is stopped.
Let's use $SYSTEMD_NETWORK_PERSISTENT_STORAGE_READY=1 instead on testing.
This introduces $SYSTEMD_KEYMAP_DIRECTORIES environment variable to
override the hardcoded keymap directories.
I think it is not necessary to provide the first class configuration
option for controlling the keymap directories, but it is not good to
hardcode the paths. So, let's introduce an environment variable to
override that.
Prompted by #31759.
Closes#31759.
This mirrors the existing CONTAINER_INTERFACE.md document, but describes
extension points of systemd running in a VM with a machine manager
supervising it.
