Merge branch 'jk/partial-clone-sparse-blob'

The name of the blob object that stores the filter specification for sparse cloning/fetching was interpreted in a wrong place in the code, causing Git to abort. * jk/partial-clone-sparse-blob: list-objects-filter: use empty string instead of NULL for sparse "base" list-objects-filter: give a more specific error sparse parsing error list-objects-filter: delay parsing of sparse oid t5616: test cloning/fetching with sparse:oid=<oid> filter