Merge branch 'ps/reftable-exclude' into ps/reftable-alloc-failures

* 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