Re: git status: small difference between stating whole repository and small subdirectory

Jeff King [off-list ref] writes:

That being said, we do have an index extension to store the tree sha1 of
whole directories (i.e., we populate it when we write a whole tree or
subtree into the index from the object db, and it becomes invalidated
when a file becomes modified). This optimization is used by things like
"git commit" to avoid having to recreate the same sub-trees over and
over when creating tree objects from the index. But we could also use it
here to avoid having to even read the sub-tree objects from the object
db.

Like b65982b (Optimize "diff-index --cached" using cache-tree, 2009-05-20)
perhaps?