Code refactoring around object database sources.
* ps/object-source-management:
odb: handle recreation of quarantine directories
odb: handle changing a repository's commondir
chdir-notify: add function to unregister listeners
odb: handle initialization of sources in `odb_new()`
http-push: stop setting up `the_repository` for each reference
t/helper: stop setting up `the_repository` repeatedly
builtin/index-pack: fix deferred fsck outside repos
oidset: introduce `oidset_equal()`
odb: move logic to disable ref updates into repo
odb: refactor `odb_clear()` to `odb_free()`
odb: adopt logic to close object databases
setup: convert `set_git_dir()` to have file scope
path: move `enter_repo()` into "setup.c"