lttng save [--all] issues misleading message when there are no sessions to save
On a freshly-booted system where no LTTng sessions have yet been created, you have this:
$ lttng list Currently no available tracing session $ lttng save --all All sessions have been saved successfully
The latter message is misleading because nothing has been saved anywhere.
lttng save [--all] should detect the no-sessions case and respond like
lttng list does, by stating '
Currently no tracing sessions to save'.
As an aside, both
lttng list and
lttng save should probably return error code 4 (command warning) when there are no sessions.
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