Patch Set 4: Looks good to me, but someone else must approve; IP review completed

I think we want this in 0.9 because otherwise large objects stored as deltas in packs can be incredibly slow to access, especially if they are accessed often.

The downside is, when checking out a large object into the local working directory, we're also deflating it as a loose object just in case we need to re-read that content in the future.  Large binary objects are probably less frequently modified by the user in the working directory, so we're probably less likely to actually need this faster access.  So we might be doing too much work in some cases.

But for a gerrit code review server serving large binary files, this really helps, because users of the server tend to access the same objects several times before the next git gc runs.