Merge branch 'kn/for-each-ref-skip-updates'

Code clean-up. * kn/for-each-ref-skip-updates: ref-filter: use REF_ITERATOR_SEEK_SET_PREFIX instead of '1' t6302: add test combining '--start-after' with '--exclude' for-each-ref: reword the documentation for '--start-after' for-each-ref: fix documentation argument ordering ref-cache: use 'size_t' instead of int for length