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

git-submodule.sh

@@ -1127,6 +1127,11 @@ cmd_sync()
 	done
 }
 
+cmd_absorbgitdirs()
+{
+	git submodule--helper absorb-git-dirs --prefix "$wt_prefix" "$@"
+}
+
 # This loop parses the command line arguments to find the
 # subcommand name to dispatch.  Parsing of the subcommand specific
 # options are primarily done by the subcommand implementations.
@@ -1136,7 +1141,7 @@ cmd_sync()
 while test $# != 0 && test -z "$command"
 do
 	case "$1" in
-	add | foreach | init | deinit | update | status | summary | sync)
+	add | foreach | init | deinit | update | status | summary | sync | absorbgitdirs)
 		command=$1
 		;;
 	-q|--quiet)