Extending ostree's functionality (adding a metadat index)

[Vivek Dasmohapatra <vivek collabora co uk>]

Hi -

I've been given the task of investigating ostree, and adding an index
to it so that a client can efficiently determine how big a download
of a given commit would be (without downloading all the individual
metadata files).

Our current idea is to add a new index object which holds the relevant
data and I was wondering if the ostree developers would be interested
in merging this work and/or had any pointers or suggestions: Do you think
this is a viable (and reasonable) approach? If not, what would your 
suggestion(s) be?