Merge branch 'ps/reftable-exclude'

The reftable backend learned to more efficiently handle exclude patterns while enumerating the refs. * ps/reftable-exclude: refs/reftable: wire up support for exclude patterns reftable/reader: make table iterator reseekable t/unit-tests: introduce reftable library Makefile: stop listing test library objects twice builtin/receive-pack: fix exclude patterns when announcing refs refs: properly apply exclude patterns to namespaced refs