Hi Javier. Here I attach a first not-yet-draft chapter of Metacello. There you will find the answer ;)�� (feedback is welcome!!!)

But in sumary, you should commit to the repository of the same project. In your case, as Igor said, to GLMorphic repository.
There you can commit your development changes to the configuration. Once you have a released version, you just copy it to MetacelloConfiguration repository.

Cheers

Mariano


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