Merge branch 'ps/the-index-is-no-more'

Merge branch 'ps/the-index-is-no-more'

The singleton index_state instance "the_index" has been eliminated
by always instantiating "the_repository" and replacing references
to "the_index"  with references to its .index member.

* ps/the-index-is-no-more:
  repository: drop `initialize_the_repository()`
  repository: drop `the_index` variable
  builtin/clone: stop using `the_index`
  repository: initialize index in `repo_init()`
  builtin: stop using `the_index`
  t/helper: stop using `the_index`