Evaluate not having / having a default --index value for the `sysand publish` command

[consideRatio]

We have a default index when reading, but not when publishing with sysand publish.

There is a case to be made that its worth being explicit when publishing, because its a write operation that is worth being intentional about.

Not sure what I think, so unless we form a clearer opinion togehter we should probably not make any change.