Merge branch 'jk/reflog-special-cases-fix'

The logic to access reflog entries by date and number had ugly corner cases at the boundaries, which have been cleaned up. * jk/reflog-special-cases-fix: read_ref_at(): special-case ref@{0} for an empty reflog get_oid_basic(): special-case ref@{n} for oldest reflog entry Revert "refs: allow @{n} to work with n-sized reflog"