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`