tree 83e73be457e2ce722d73e4211b61942ee45ae89e
parent dceedbcd6e66d60f095aacfa308055b7ca6f45a7
author Jonathan Nieder <jrn@google.com> 1596075531 -0700
committer Jonathan Nieder <jrn@google.com> 1596081860 -0700

Do not send empty blob in response to blob:none filter

If I create a repository containing an empty file and clone it
with

	git clone --no-checkout --filter=blob:none \
		https://url/of/repository

then I would expect no blobs to be transferred over the wire.  Alas,
JGit rewrites filter=blob:none to filter=blob:limit=0, so if the
repository contains an empty file then the empty blob gets
transferred.

Fix it by teaching JGit about filters based on object type to
complement the existing filters based on object size.  This prepares
us for other future filters such as object:none.

In particular, this means we do not need to look up the size of the
filtered blobs, which should speed up clones.  Noticed by Anna
Pologova and Terry Parker.

Change-Id: Id4b234921a190c108d8be2c87f54dcbfa811602a
Signed-off-by: Jonathan Nieder <jrn@google.com>