Limiting multi-choice options in child based on Parent selections?

[Jordan Janis]

Here's the scenario:

We have a multi-choice custom field called Marketplace.  Not surprisingly, it has values such as, US, UK, DE, FR, AU, CA, etc.  About 15 options total.  The parent issue defines what markets in which a particular feature will be deployed.  Child issues will be specific to one or more of those markets representing the work specific to a particular market. 

We want to be able to limit which marketplaces can be selected from within the child issues.

So, for example, if in the parent issue the value of Marketplace is "US, UK, CA, AU" then the available options for Marketplace for all of its children should be "US, UK, CA, AU" - not the fill list of fifteen.