The `head` subcommand should decide on a multiple file strategy

[jobarr-amzn]

Standard invocations of head add a header per file emitted. We may want to do that, but we need to consider the implications when using ion head in part of a value pipeline.

Should the header be Ion data? How can it be distinguished from the other text data? Should we use different headers or not depending on the specified --format, e.g. should --format lines use the standard head file header of ====> Filename <=== or whatever it does, while --format pretty uses an Ion value and --format text or --format binary do nothing?

Lots of questions here.

https://linux.die.net/man/1/head