[ENH] Specify echo and run indices are nonnegative integers in schema

[tsalo]

This incorporates the changes in #535 to the definitions for the echo and run entities to the schema. I should have commented directly on #535 about this, but I didn't think of it until this morning.

[sappelhoff]

good catch @tsalo

[nicholst]

Good catch... does illustrate the attentiveness needed to keep the schema up to date.

Aside from the anal comment about typesetting keywords, this looks good to go.

[tsalo]

Good catch... does illustrate the attentiveness needed to keep the schema up to date.

Very true, but once we are able to render the specification text from the schema (e.g., #568), then we'll be back to having to only update definitions in one location. Until then, I'll try to pay closer attention to any PRs that impact entities.

[effigies]

We could add a quick test that just greps through the entire source for these description texts.

[tsalo]

@effigies I'll open a new issue for that and merge this. Thanks all!

[sappelhoff]

@nicholst I just realized that we probably missed a definition in the "common principles" section.

See: https://bids-specification.readthedocs.io/en/latest/02-common-principles.html#definitions

under point 9:

<index> - a numeric value, possibly prefixed with arbitrary number of 0s for consistent indentation, e.g., it is 01 in run-01 following run- specification.

should this become a nonnegative numeric value ? cc @tsalo @effigies

[nicholst]

Yes @sappelhoff ! Better yet, specify that it's an integer: <index> - a nonnegative integer ... right? We don't want decimals, right?

[sappelhoff]

Better yet, specify that it's an integer: - a nonnegative integer ... right? We don't want decimals, right?

agreed!