There are two overloads, so that it can use the operational
target when a target property is being evaluated, and a target
can alternatively be specified by name.
At this point, the generators don't chain. That comes later.
Generator expressions for comparing strings, evaluating
strings as booleans, and for creating literal right-angle-brackets
and commas are added. Those may be needed in some cases
where they appear in literals.
This expression evaluates to '1' or '0' to indicate whether the build
configuration for which the expression is evaluated matches tha named
configuration. In combination with the "$<0:...>" and "$<1:...>"
expressions this allows per-configuration content to be generated.
Add generator expressions that combine and use boolean test results:
$<0:...> = empty string (ignores "...")
$<1:...> = content of "..."
$<AND:?[,?]...> = '1' if all '?' are '1', else '0'
$<OR:?[,?]...> = '0' if all '?' are '0', else '1'
$<NOT:?> = '0' if '?' is '1', else '1'
These will be useful to evaluate (future) boolean query expressions and
condition content on the results. Include tests and documentation.