Merge branch 'ar/test-cleanup-unused-file-creation'

Test clean-up. * ar/test-cleanup-unused-file-creation: t1507: assert output of rev-parse t1404: don't create unused file t1400: assert output of update-ref t1302: don't create unused file t1010: don't create unused files t1006: assert error output of cat-file t1005: assert output of ls-files