Previously we made a very generic suggestion to use -target to split a
change into two parts as a workaround for the fact that count and for_each
must be known during planning. That works, but we didn't have enough
information available to tell the operator exactly what to target and so
anyone who is not an expert on the configuration they're working with tends
to get stuck unable to figure out exactly what they need to do.
The new -exclude option gives us an opportunity to do better here: we tend
to know for which object we're currently evaluating count or for_each, and
so we can mention that object directly in the error message when if we
recommend to use -exclude instead of -target.
Not all objects that support count/for_each will necessarily be directly
targetable, so we can still potentially recommend -target when we're
dealing with one of those objects. For example, as of this commit that
is true for for_each in a provider block, because there is not currently
any syntax for specifying a provider configuration as an addrs.Targetable.
Perhaps we'll introduce such a thing in the future, but that's outside the
scope of this change that's primarily focused on improving the messaging
for resource and module count/for_each.
Signed-off-by: Martin Atkins <mart@degeneration.co.uk>
