Rename `marks` to `mark`?

[aadcg]

#2520 introduced marks-actions, which adds to return-actions and selection-actions.

However, marks-actions sounds really weird and it's hard to pronounce.

I'd rename marks to mark. Indeed, selection and mark are radically different since the former is always a singleton but the latter isn't. They're actually both lists, but for very different reasons related to the way they're implemented.

It doesn't sound odd to me that mark would a be concept defined by a word in the singular form that refers to a set of entities.

[aadcg]

On second thoughts, I'd suggest something even more radical.

We have the following concepts: suggestions, selection and marks.

Wouldn't it be saner to have suggestions, current-suggestion and selection?

Suggestions are the prompt options; current-suggestion is a singleton of suggestions; and selection is a subset of suggestions.

[aartaka]

I guess the initial naming comes from Helm. If the new naming is drains less cognitive resources, then why not :)

I'll leave that to @Ambrevar, though, as he wanted to abstract promtper into a separate library, and that is likely when the renaming should happen.

[Ambrevar]

Yes, the naming comes from Helm. "Mark" is not very familiar outside of this context, so yes, I'm in favour of André's renaming suggestion.

Shall it wait for 4.0 though? We've already got a lot on our hands...

[aadcg]

Yes, this is not particularly important.