Merge branch 'vd/for-each-ref-unsorted-optimization'

Merge branch 'vd/for-each-ref-unsorted-optimization'

"git for-each-ref --no-sort" still sorted the refs alphabetically
which paid non-trivial cost.  It has been redefined to show output
in an unspecified order, to allow certain optimizations to take
advantage of.

* vd/for-each-ref-unsorted-optimization:
  t/perf: add perf tests for for-each-ref
  ref-filter.c: use peeled tag for '*' format fields
  for-each-ref: clean up documentation of --format
  ref-filter.c: filter & format refs in the same callback
  ref-filter.c: refactor to create common helper functions
  ref-filter.c: rename 'ref_filter_handler()' to 'filter_one()'
  ref-filter.h: add functions for filter/format & format-only
  ref-filter.h: move contains caches into filter
  ref-filter.h: add max_count and omit_empty to ref_format
  ref-filter.c: really don't sort when using --no-sort