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

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