I had a chat with Timo in person about this patch:
https://gerrit.wikimedia.org/r/111250
He still feels strongly that adding this to core in a generic blob
form is not very helpful and adding it to core without a standard
JavaScript templating library would also be an incomplete job.
As a result, it seems the best way forward might me to move the code
that MobileFrontend is using for this into an extension
MediaWikiTemplates that both Flow and MobileFrontend can depend on.
We'll make a few modifications to it so it supports both template
libraries - Hogan and Handlebars.
This would allow code sharing and iteration on the code and hopefully
will lend itself nicely as a shared repository where we can experiment
with different templating languages.
Thoughts?