"git checkout" is taught the "--recurse-submodules" option.
* sb/checkout-recurse-submodules:
builtin/read-tree: add --recurse-submodules switch
builtin/checkout: add --recurse-submodules switch
entry.c: create submodules when interesting
unpack-trees: check if we can perform the operation for submodules
unpack-trees: pass old oid to verify_clean_submodule
update submodules: add submodule_move_head
submodule.c: get_super_prefix_or_empty
update submodules: move up prepare_submodule_repo_env
submodules: introduce check to see whether to touch a submodule
update submodules: add a config option to determine if submodules are updated
update submodules: add submodule config parsing
make is_submodule_populated gently
lib-submodule-update.sh: define tests for recursing into submodules
lib-submodule-update.sh: replace sha1 by hash
lib-submodule-update: teach test_submodule_content the -C <dir> flag
lib-submodule-update.sh: do not use ./. as submodule remote
lib-submodule-update.sh: reorder create_lib_submodule_repo
submodule--helper.c: remove duplicate code
connect_work_tree_and_git_dir: safely create leading directories