Merge branch 'ab/fewer-the-index-macros'

Merge branch 'ab/fewer-the-index-macros'

Progress on removing 'the_index' convenience wrappers.

* ab/fewer-the-index-macros:
  cocci: apply "pending" index-compatibility to some "builtin/*.c"
  cache.h & test-tool.h: add & use "USE_THE_INDEX_VARIABLE"
  {builtin/*,repository}.c: add & use "USE_THE_INDEX_VARIABLE"
  cocci: apply "pending" index-compatibility to "t/helper/*.c"
  cocci & cache.h: apply variable section of "pending" index-compatibility
  cocci & cache.h: apply a selection of "pending" index-compatibility
  cocci: add a index-compatibility.pending.cocci
  read-cache API & users: make discard_index() return void
  cocci & cache.h: remove rarely used "the_index" compat macros
  builtin/{grep,log}.: don't define "USE_THE_INDEX_COMPATIBILITY_MACROS"
  cache.h: remove unused "the_index" compat macros