Merge branch 'jc/reffiles-tests'

Tests on ref API are moved around to prepare for reftable. * jc/reffiles-tests: t5312: move reffiles specific tests to t0601 t4202: move reffiles specific tests to t0600 t3903: make drop stash test ref backend agnostic t1503: move reffiles specific tests to t0600 t1415: move reffiles specific tests to t0601 t1410: move reffiles specific tests to t0600 t1406: move reffiles specific tests to t0600 t1405: move reffiles specific tests to t0601 t1404: move reffiles specific tests to t0600 t1414: convert test to use Git commands instead of writing refs manually remove REFFILES prerequisite for some tests in t1405 and t2017 t3210: move to t0601