DLMSEP#1: avoid need to specify 'metadata[]' in --output-format

[yarikoptic]

DLMSEP - DataLad Metadata Search Enhancement Proposal

Possibly ignorant idea -- since

• all the keys in meta-data should be (?) coming from a specific ontology, they would always have "ontology:" prefix and thus never collide with native fields.
• --show-keys lists them without metadata[] wrapper

it makes only sense to be able to specify output format without needing metadata[] since that one could be flattened into the record dictionary imho

[mih]

This would be nice, but would also require a much more stringent result dict management within datalad (apart from metadata functionality). Metadata keys are not guaranteed to come with a prefix, and result dict keys are not guaranteed to not be in conflict with what an arbitrary parser returns as keys.

Moreover, the search result dict carries more than metadata. For example, info on what actually matched. This would also need to be managed in a flat structure.

So, as soon as we have a comprehensive vocabulary of DataLad's own (internal!) terms we can do that. And at the same time, we can add tests that validate any generated result for compliance with this vocabulary.

I am in favor of that, but it is not done with by changing a few lines.