Some features from "git tag -l" and "git branch -l" have been made
available to "git for-each-ref" so that eventually the unified
implementation can be shared across all three, in a follow-up
series or two.

* kn/for-each-tag-branch:
  for-each-ref: add '--contains' option
  ref-filter: implement '--contains' option
  parse-options.h: add macros for '--contains' option
  parse-option: rename parse_opt_with_commit()
  for-each-ref: add '--merged' and '--no-merged' options
  ref-filter: implement '--merged' and '--no-merged' options
  ref-filter: add parse_opt_merge_filter()
  for-each-ref: add '--points-at' option
  ref-filter: implement '--points-at' option
  tag: libify parse_opt_points_at()
  t6302: for-each-ref tests for ref-filter APIs