Merge branch 'hn/refs-test-cleanup'

A handful of tests that assumed implementation details of files backend for refs have been cleaned up. * hn/refs-test-cleanup: t6001: avoid direct file system access t6500: use "ls -1" to snapshot ref database state t7064: use update-ref -d to remove upstream branch t1410: mark test as REFFILES t1405: mark test for 'git pack-refs' as REFFILES t1405: use 'git reflog exists' to check reflog existence t2402: use ref-store test helper to create broken symlink t3320: use git-symbolic-ref rather than filesystem access t6120: use git-update-ref rather than filesystem access t1503: mark symlink test as REFFILES t6050: use git-update-ref rather than filesystem access