Merge branch 'nd/remove-ignore-env-field'

Code clean-up for the "repository" abstraction.

* nd/remove-ignore-env-field:
repository.h: add comment and clarify repo_set_gitdir
repository: delete ignore_env member
sha1_file.c: move delayed getenv(altdb) back to setup_git_env()
repository.c: delete dead functions
repository.c: move env-related setup code back to environment.c
repository: initialize the_repository in main()

diff --cc cache.h
Simple merge

diff --cc environment.c
Simple merge

diff --cc setup.c
Simple merge

diff --cc sha1_file.c
Simple merge