Merge branch 'sb/submodule-embed-gitdir'

A new submodule helper "git submodule embedgitdirs" to make it easier to move embedded .git/ directory for submodules in a superproject to .git/modules/ (and point the latter with the former that is turned into a "gitdir:" file) has been added. * sb/submodule-embed-gitdir: worktree: initialize return value for submodule_uses_worktrees submodule: add absorb-git-dir function move connect_work_tree_and_git_dir to dir.h worktree: check if a submodule uses worktrees test-lib-functions.sh: teach test_commit -C <dir> submodule helper: support super prefix submodule: use absolute path for computing relative path connecting