Generate file structures on dynamic loop

[yajo]

Just: {% yield single_var from looped_var %}{{ single_var }}{% endyield %}

The implementation could be similar to https://github.com/orgs/copier-org/discussions/908#discussioncomment-6505536:

Does single_var exist in context?

• yes: do nothing special
• no: raise YieldException("single_var", looped_var)

OK, we got the exception. Now, are you rendering a filename?

• Yes: start loop. Inject single_var in the context and keep rendering the contents (of the dir/file, recursively).
• No: just let the exception raise and print a nice message "Using yield outside of file names isn't supported".

Originally posted by @yajo in #908 (reply in thread)

[0xsoydev]

Hello there @yajo, I am new to the open source community, I would like to try and solve this issue, if you may, could you please assign this issue to me?

[kj-9]

@yajo
Hi, I've created #1855 to implement the yield tag functionality. Would you kindly review and provide advice?

I'm new to Copier and don't have deep knowledge of the codebase yet, so I'm not entirely confident if this implementation is the best approach.

I'm really looking forward to having this feature available, and I hope this contribution can help move it forward. Any feedback would be greatly appreciated!