Merge branch 'sb/checkout-recurse-submodules'

"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

diff --cc builtin/checkout.c
Simple merge

diff --cc builtin/grep.c
Simple merge

diff --cc builtin/submodule--helper.c
Simple merge

diff --cc dir.c
index 837ff96,6f52af7..f451bfa
--- 1/dir.c
--- 2/dir.c
+++ b/dir.c
@@@ -2765,23 -2728,33 +2765,33 @@@ void untracked_cache_add_to_index(struc
  /* Update gitfile and core.worktree setting to connect work tree and git dir */
  void connect_work_tree_and_git_dir(const char *work_tree_, const char *git_dir_)
  {
-       struct strbuf file_name = STRBUF_INIT;
+       struct strbuf gitfile_sb = STRBUF_INIT;
+       struct strbuf cfg_sb = STRBUF_INIT;
        struct strbuf rel_path = STRBUF_INIT;
-       char *git_dir = real_pathdup(git_dir_, 1);
-       char *work_tree = real_pathdup(work_tree_, 1);
+       char *git_dir, *work_tree;
  
-       /* Update gitfile */
-       strbuf_addf(&file_name, "%s/.git", work_tree);
-       write_file(file_name.buf, "gitdir: %s",
-                  relative_path(git_dir, work_tree, &rel_path));
+       /* Prepare .git file */
+       strbuf_addf(&gitfile_sb, "%s/.git", work_tree_);
+       if (safe_create_leading_directories_const(gitfile_sb.buf))
+               die(_("could not create directories for %s"), gitfile_sb.buf);
+ 
+       /* Prepare config file */
+       strbuf_addf(&cfg_sb, "%s/config", git_dir_);
+       if (safe_create_leading_directories_const(cfg_sb.buf))
+               die(_("could not create directories for %s"), cfg_sb.buf);
  
 -      git_dir = real_pathdup(git_dir_);
 -      work_tree = real_pathdup(work_tree_);
++      git_dir = real_pathdup(git_dir_, 1);
++      work_tree = real_pathdup(work_tree_, 1);
+ 
+       /* Write .git file */
+       write_file(gitfile_sb.buf, "gitdir: %s",
+                  relative_path(git_dir, work_tree, &rel_path));
        /* Update core.worktree setting */
-       strbuf_reset(&file_name);
-       strbuf_addf(&file_name, "%s/config", git_dir);
-       git_config_set_in_file(file_name.buf, "core.worktree",
+       git_config_set_in_file(cfg_sb.buf, "core.worktree",
                               relative_path(work_tree, git_dir, &rel_path));
  
-       strbuf_release(&file_name);
+       strbuf_release(&gitfile_sb);
+       strbuf_release(&cfg_sb);
        strbuf_release(&rel_path);
        free(work_tree);
        free(git_dir);

diff --cc submodule-config.c
Simple merge

diff --cc submodule.c
index 3200b7b,6e8825b..040f4c2
--- 1/submodule.c
--- 2/submodule.c
+++ b/submodule.c
@@@ -1412,13 -1581,10 +1581,10 @@@ static void relocate_single_git_dir_int
        new_git_dir = git_path("modules/%s", sub->name);
        if (safe_create_leading_directories_const(new_git_dir) < 0)
                die(_("could not create directory '%s'"), new_git_dir);
 -      real_new_git_dir = real_pathdup(new_git_dir);
 +      real_new_git_dir = real_pathdup(new_git_dir, 1);
  
-       if (!prefix)
-               prefix = get_super_prefix();
- 
        fprintf(stderr, _("Migrating git directory of '%s%s' from\n'%s' to\n'%s'\n"),
-               prefix ? prefix : "", path,
+               get_super_prefix_or_empty(), path,
                real_old_git_dir, real_new_git_dir);
  
        relocate_gitdir(path, real_old_git_dir, real_new_git_dir);
@@@ -1469,17 -1633,12 +1633,12 @@@ void absorb_git_dir_into_superproject(c
                sub = submodule_from_path(null_sha1, path);
                if (!sub)
                        die(_("could not lookup name for submodule '%s'"), path);
-               new_git_dir = git_path("modules/%s", sub->name);
-               if (safe_create_leading_directories_const(new_git_dir) < 0)
-                       die(_("could not create directory '%s'"), new_git_dir);
-               real_new_git_dir = real_pathdup(new_git_dir, 1);
-               connect_work_tree_and_git_dir(path, real_new_git_dir);
- 
-               free(real_new_git_dir);
+               connect_work_tree_and_git_dir(path,
+                       git_path("modules/%s", sub->name));
        } else {
                /* Is it already absorbed into the superprojects git dir? */
 -              char *real_sub_git_dir = real_pathdup(sub_git_dir);
 -              char *real_common_git_dir = real_pathdup(get_git_common_dir());
 +              char *real_sub_git_dir = real_pathdup(sub_git_dir, 1);
 +              char *real_common_git_dir = real_pathdup(get_git_common_dir(), 1);
  
                if (!starts_with(real_sub_git_dir, real_common_git_dir))
                        relocate_single_git_dir_into_superproject(prefix, path);

diff --cc submodule.h
Simple merge