Generalize String criteria matching

[earboxer]

Closes #306

Most string fields have been changed to support

• Regex matching [app-name~=D..o]
• Not equal to [summary!=""]
• Bare specification [summary] (equivalent to [summary!=""])
• Bare negation [!summary] (equivalent to [summary=""])

[earboxer]

I included the operator OP_NONE, but it's not being used.

Originally I was thinking this could replace the 'spec' definitions, but didn't dig deep enough to see if this is the case or not...

[emersion]

Thanks for the patch! Sorry I took way too much time to get back to this.

I think it's a bit confusing to introduce all of these new operators, but only support them on strings. For instance truthy/falsy are not supported on booleans.

Maybe operators could be introduced incrementally on all types they make sense, starting with e.g. regexp which only makes sense on strings.

[emersion]

This is specific to strings, maybe should be renamed to e.g. struct mako_string_criteria?

[earboxer]

I think I was originally thinking that mako_condition could be used for all of the conditions (and maybe there are other operators that other types of conditions could use, like "in" or "less than"/"greater than" for urgency, group-index).

Since this PR is "Generalize String criteria matching", I didn't want to go too far out of scope and refactor all of the conditions.

But I'm not too invested in this, so if you really want the rename, I will probably do it.

[emersion]

How would that work? The value field is a char *, but we'd need some other type for urgency/group-index/etc.