"git for-each-ref" learns "--start-after" option to help
applications that want to page its output.
* kn/for-each-ref-skip:
ref-cache: set prefix_state when seeking
for-each-ref: introduce a '--start-after' option
ref-filter: remove unnecessary else clause
refs: selectively set prefix in the seek functions
ref-cache: remove unused function 'find_ref_entry()'
refs: expose `ref_iterator` via 'refs.h'
8d9f536a51