Merge branch 'rs/test-cleanup'

Test cleanup.

* rs/test-cleanup:
  t7811: don't create unused file
  t9300: don't create unused file
  test: use test_must_be_empty F instead of test_cmp empty F
  test: use test_must_be_empty F instead of test -z $(cat F)
  t1400: use test_must_be_empty
  t1410: use test_line_count
  t1512: use test_line_count

diff --cc t/t1400-update-ref.sh
Simple merge

diff --cc t/t1512-rev-parse-disambiguation.sh
Simple merge