`--label-file` has the exact same behavior as `--env-file`, meaning any
placeholder (i.e. a simple key, no `=` sign, no value), it will get the
value from the environment variable.
For `--label-file` it should just add an empty label.
Signed-off-by: Vincent Demeester <vincent@sbr.pm>
Upstream-commit: 2b17f4c8a8
Component: cli
