Merge branch 'rs/parse-options-duplicated-long-options'

The parse-options API learned to notice an options[] array with
duplicated long options.

* rs/parse-options-duplicated-long-options:
  parseopt: check for duplicate long names and numerical options
  pack-objects: remove duplicate --stdin-packs definition

diff --cc builtin/pack-objects.c
Simple merge

diff --cc parse-options.c
Simple merge