Merge branch 'cp/unit-test-reftable-stack' into ps/reftable-exclude

* cp/unit-test-reftable-stack: t-reftable-stack: add test for stack iterators t-reftable-stack: add test for non-default compaction factor t-reftable-stack: use reftable_ref_record_equal() to compare ref records t-reftable-stack: use Git's tempfile API instead of mkstemp() t: harmonize t-reftable-stack.c with coding guidelines t: move reftable/stack_test.c to the unit testing framework