The howto doesn't create just one but a multitude of transformers

[retog]

This might be a bit night-picking: the HowTo doesn't just create "a transformer" but a multitude of transformer, actually one for every possible sed-expression.

It might be worth writing that a transformer always take just one input and that configuration is typically encoded in the URI, so that one - strictly speaking - doesn't has one but many transformers.

[gmega]

Yes, you are right. I'm thinking that this requires somewhat of a rewrite of the whole thing introducing the now formalized notion of a transformer factory as well. For now, I'll patch in a snippet of text warning the reader that this is not really a transformer in the strictest sense, and we can open a bug on the next sprint for me to rewrite things

[gmega]

OK, here goes the new section with the distinction:

https://github.com/fusepoolP3/p3-transformer-howto/blob/master/transformer-howto.md#transformer-or-transformer-factory

for now it's somewhat patched in.