Merge branch 'cc/rev-list-allow-missing-tips'

"git rev-list --missing=print" has learned to optionally take "--allow-missing-tips", which allows the objects at the starting points to be missing. * cc/rev-list-allow-missing-tips: revision: fix --missing=[print|allow*] for annotated tags rev-list: allow missing tips with --missing=[print|allow*] t6022: fix 'test' style and 'even though' typo oidset: refactor oidset_insert_from_set() revision: clarify a 'return NULL' in get_reference()