The upstream systemd git repo only contains the main systemd branch that
progresses at a quick pace, continuously bringing both bugfixes and new features.
Distributions usually prefer basing their releases on stabilized versions
that receive the bugfixes but not the features.
(From OE-Core master rev: c21bf9d7bb0cb90392ed50a44c57a3d068b88ef9)
(From OE-Core rev: c3da0d750ce7b45fee9db3e985f585f5fb2e193d)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>