Re: Extending ostree's functionality (adding a metadat index)

[Vivek Dasmohapatra <vivek collabora co uk>]

> Also with the first change:
> http://cgit.collabora.com/git/user/vivek/ostree.git/commit/?h=commit-index-ii&id=b7924c99243ade253b26317a77b4449d380a39c5
> I think it'd be best if we compute the sizes just before writing out the
> commit object, by traversing the tree again.  As opposed to gathering
> the information in stage_object().   The problem is
> that if say you do a commit like this:
>
> $ mkdir overlay
> $ touch overlay/usr/bin/foo
> $ ostree commit -b --tree=ref=gnome-ostree/buildmaster/x86_64-runtime --tree=dir=overlay
>
> We'll only end up writing .sizes that contains the object usr/bin/foo, because
> the commit logic there won't call stage_object() for everything that's already in
> gnome-ostree/buildmaster/x86_64-runtime.

Not quite, because the next commit adds the copy of the sizes from the existing
ref into the new commit's size cache, so that committing from multiple refs 
still produces a size cache.

I suppose another problem arises because the overlay might contain files
with the same paths, so we need to de-dupe by path as well as checksum
so that the size cacheis accurate.