[WIP PATCH 0/4] Recursively checkout submodules

@@ -2827,6 +2827,7 @@ static int check_preimage(struct patch *patch, struct cache_entry **ce, struct s
 			costate.quiet = 0;
 			costate.not_new = 0;
 			costate.refresh_cache = 1;
+			costate.ignore_submodules = 1;
 			if (checkout_entry(*ce, &costate, NULL) ||
 			    lstat(old_name, st))
 				return -1;

@@ -254,6 +254,7 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
 	state.force = force;
 	state.quiet = quiet;
 	state.not_new = not_new;
+	state.ignore_submodules = 1;

 	if (state.base_dir_len || to_tempfile) {
 		/* when --prefix is specified we do not

@@ -248,6 +248,7 @@ static int checkout_paths(struct tree *source_tree, const char **pathspec,
 	memset(&state, 0, sizeof(state));
 	state.force = 1;
 	state.refresh_cache = 1;
+	state.ignore_submodules = 1;
 	for (pos = 0; pos < active_nr; pos++) {
 		struct cache_entry *ce = active_cache[pos];
 		if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {

@@ -802,7 +802,8 @@ struct checkout {
 	unsigned force:1,
 		 quiet:1,
 		 not_new:1,
-		 refresh_cache:1;
+		 refresh_cache:1,
+		 ignore_submodules:1;
 };

 extern int checkout_entry(struct cache_entry *ce, const struct checkout *state, char *topath);

@@ -1,6 +1,7 @@
 #include "cache.h"
 #include "blob.h"
 #include "dir.h"
+#include "submodule.h"

 static void create_directories(const char *path, int path_len,
 			       const struct checkout *state)

@@ -222,9 +223,11 @@ int checkout_entry(struct cache_entry *ce, const struct checkout *state, char *t
 		 * just do the right thing)
 		 */
 		if (S_ISDIR(st.st_mode)) {
-			/* If it is a gitlink, leave it alone! */
-			if (S_ISGITLINK(ce->ce_mode))
-				return 0;
+			if (S_ISGITLINK(ce->ce_mode)) {
+				if (state->ignore_submodules)
+					return 0;
+				return checkout_submodule(ce->name, ce->sha1, state->force);
+	       		}
 			if (!state->force)
 				return error("%s is a directory", path);
 			remove_subtree(path);

@@ -206,3 +206,35 @@ unsigned is_submodule_modified(const char *path, int ignore_untracked)
 	strbuf_release(&buf);
 	return dirty_submodule;
 }
+
+int checkout_submodule(const char *path, const unsigned char sha1[20], int force)
+{
+	struct strbuf buf = STRBUF_INIT;
+	struct child_process cp;
+	const char *hex_sha1 = sha1_to_hex(sha1);
+	const char *argv[] = {
+		"checkout",
+                force ? "-qf" : "-q",
+		hex_sha1,
+		NULL,
+	};
+	
+	strbuf_addf(&buf, "%s/.git/", path);
+	if (!is_directory(buf.buf)) {
+		strbuf_release(&buf);
+		/* The submodule is not populated, so we can't check it out */
+		return 0;
+	}
+
+	memset(&cp, 0, sizeof(cp));
+	cp.argv = argv;
+	cp.env = local_repo_env;
+	cp.git_cmd = 1;
+	cp.no_stdin = 1;
+	cp.out = -1;
+	cp.dir = path;   /* GIT_WORK_TREE doesn't work for git checkout */
+	if (run_command(&cp))
+		return error("Could not checkout submodule %s", path);
+
+	return 0;
+}

@@ -6,5 +6,6 @@ void show_submodule_summary(FILE *f, const char *path,
 		unsigned dirty_submodule,
 		const char *del, const char *add, const char *reset);
 unsigned is_submodule_modified(const char *path, int ignore_untracked);
+int checkout_submodule(const char *path, const unsigned char sha1[20], int force);

 #endif

@@ -711,6 +711,7 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 	state.force = 1;
 	state.quiet = 1;
 	state.refresh_cache = 1;
+	state.ignore_submodules = 1;

 	memset(&el, 0, sizeof(el));
 	if (!core_apply_sparse_checkout || !o->update)

@@ -184,6 +184,7 @@ int write_archive_entries(struct archiver_args *args,
 		opts.src_index = &the_index;
 		opts.dst_index = &the_index;
 		opts.fn = oneway_merge;
+		opts.ignore_submodules = 1;
 		init_tree_desc(&t, args->tree->buffer, args->tree->size);
 		if (unpack_trees(1, &t, &opts))
 			return -1;

@@ -637,6 +637,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
 		opts.verbose_update = (option_verbosity > 0);
 		opts.src_index = &the_index;
 		opts.dst_index = &the_index;
+		opts.ignore_submodules = 1;

 		tree = parse_tree_indirect(our_head_points_at->old_sha1);
 		parse_tree(tree);

@@ -257,6 +257,7 @@ static void create_base_index(void)
 	opts.dst_index = &the_index;

 	opts.fn = oneway_merge;
+	opts.ignore_submodules = 1;
 	tree = parse_tree_indirect(head_sha1);
 	if (!tree)
 		die("failed to unpack HEAD tree object");

@@ -532,6 +532,7 @@ static int read_tree_trivial(unsigned char *common, unsigned char *head,
 	if (!trees[nr_trees++])
 		return -1;
 	opts.fn = threeway_merge;
+	opts.ignore_submodules = 1;
 	cache_tree_free(&active_cache_tree);
 	for (i = 0; i < nr_trees; i++) {
 		parse_tree(trees[i]);

@@ -705,6 +706,7 @@ int checkout_fast_forward(const unsigned char *head, const unsigned char *remote
 	opts.merge = 1;
 	opts.fn = twoway_merge;
 	opts.msgs = get_porcelain_error_msgs();
+	opts.ignore_submodules = 1;

 	trees[nr_trees] = parse_tree_indirect(head);
 	if (!trees[nr_trees++])

@@ -201,6 +201,7 @@ int cmd_read_tree(int argc, const char **argv, const char *unused_prefix)

 	if (opts.debug_unpack)
 		opts.fn = debug_merge;
+	opts.ignore_submodules = 1;

 	cache_tree_free(&active_cache_tree);
 	for (i = 0; i < nr_trees; i++) {

@@ -98,6 +98,7 @@ static int reset_index_file(const unsigned char *sha1, int reset_type, int quiet
 		nr++;
 		opts.fn = twoway_merge;
 	}
+	opts.ignore_submodules = 1;

 	if (!fill_tree_descriptor(desc + nr - 1, sha1))
 		return error("Failed to find tree of %s.", sha1_to_hex(sha1));

@@ -451,6 +451,7 @@ int run_diff_index(struct rev_info *revs, int cached)
 	opts.unpack_data = revs;
 	opts.src_index = &the_index;
 	opts.dst_index = NULL;
+	opts.ignore_submodules = 1;

 	init_tree_desc(&t, tree->buffer, tree->size);
 	if (unpack_trees(1, &t, &opts))

@@ -509,6 +510,7 @@ int do_diff_cache(const unsigned char *tree_sha1, struct diff_options *opt)
 	opts.unpack_data = &revs;
 	opts.src_index = &the_index;
 	opts.dst_index = &the_index;
+	opts.ignore_submodules = 1;

 	init_tree_desc(&t, tree->buffer, tree->size);
 	if (unpack_trees(1, &t, &opts))

@@ -186,6 +186,7 @@ static int git_merge_trees(int index_only,
 	opts.src_index = &the_index;
 	opts.dst_index = &the_index;
 	opts.msgs = get_porcelain_error_msgs();
+	opts.ignore_submodules = 1;

 	init_tree_desc_from_tree(t+0, common);
 	init_tree_desc_from_tree(t+1, head);

@@ -711,7 +711,7 @@ int unpack_trees(unsigned len, struct tree_desc *t, struct unpack_trees_options
 	state.force = 1;
 	state.quiet = 1;
 	state.refresh_cache = 1;
-	state.ignore_submodules = 1;
+	state.ignore_submodules = o->ignore_submodules;

 	memset(&el, 0, sizeof(el));
 	if (!core_apply_sparse_checkout || !o->update)

@@ -33,7 +33,8 @@ struct unpack_trees_options {
 		     diff_index_cached,
 		     debug_unpack,
 		     skip_sparse_checkout,
-		     gently;
+		     gently,
+		     ignore_submodules;
 	const char *prefix;
 	int cache_bottom;
 	struct dir_struct *dir;

@@ -144,6 +144,13 @@ the conflicted merge in the specified paths.
 This means that you can use `git checkout -p` to selectively discard
 edits from your current working tree.

+--ignore-submodules::
+	Since version 1.8.0 the default behavior is to checkout populated
+	submodules recursively. When this option is used, the work trees of
+	submodules will not be updated, only the hash recorded in the
+	superproject will be changed (this was the default behavior until
+	1.8.0).
+
 <branch>::
 	Branch to checkout; if it refers to a branch (i.e., a name that,
 	when prepended with "refs/heads/", is a valid ref), then that

@@ -31,6 +31,7 @@ struct checkout_opts {
 	int force;
 	int writeout_stage;
 	int writeout_error;
+	int ignore_submodules;

 	const char *new_branch;
 	const char *new_orphan_branch;

@@ -248,7 +249,7 @@ static int checkout_paths(struct tree *source_tree, const char **pathspec,
 	memset(&state, 0, sizeof(state));
 	state.force = 1;
 	state.refresh_cache = 1;
-	state.ignore_submodules = 1;
+	state.ignore_submodules = opts->ignore_submodules;
 	for (pos = 0; pos < active_nr; pos++) {
 		struct cache_entry *ce = active_cache[pos];
 		if (match_pathspec(pathspec, ce->name, ce_namelen(ce), 0, NULL)) {

@@ -314,6 +315,7 @@ static int reset_tree(struct tree *tree, struct checkout_opts *o, int worktree)
 	opts.verbose_update = !o->quiet;
 	opts.src_index = &the_index;
 	opts.dst_index = &the_index;
+	opts.ignore_submodules = o->ignore_submodules;
 	parse_tree(tree);
 	init_tree_desc(&tree_desc, tree->buffer, tree->size);
 	switch (unpack_trees(1, &tree_desc, &opts)) {

@@ -393,6 +395,7 @@ static int merge_working_tree(struct checkout_opts *opts,
 		topts.dir = xcalloc(1, sizeof(*topts.dir));
 		topts.dir->flags |= DIR_SHOW_IGNORED;
 		topts.dir->exclude_per_dir = ".gitignore";
+		topts.ignore_submodules = opts->ignore_submodules;
 		tree = parse_tree_indirect(old->commit ?
 					   old->commit->object.sha1 :
 					   (unsigned char *)EMPTY_TREE_SHA1_BIN);

@@ -649,6 +652,8 @@ int cmd_checkout(int argc, const char **argv, const char *prefix)
 		{ OPTION_BOOLEAN, 0, "guess", &dwim_new_local_branch, NULL,
 		  "second guess 'git checkout no-such-branch'",
 		  PARSE_OPT_NOARG | PARSE_OPT_HIDDEN },
+		OPT_BOOLEAN(0, "ignore-submodules", &opts.ignore_submodules,
+			    "don't update submodule work trees"),
 		OPT_END(),
 	};
 	int has_dash_dash;

@@ -29,14 +29,24 @@ test_expect_success '"reset <submodule>" updates the index' '
 	git diff-files --quiet
 '

-test_expect_success '"checkout <submodule>" updates the index only' '
+test_expect_success '"checkout --ignore-submodules <submodule>" updates the index only' '
 	git update-index --refresh &&
 	git diff-files --quiet &&
 	git diff-index --quiet --cached HEAD &&
-	git checkout HEAD^ submodule &&
+	git checkout --ignore-submodules HEAD^ submodule &&
 	test_must_fail git diff-files --quiet &&
 	git checkout HEAD submodule &&
 	git diff-files --quiet
 '

+test_expect_success '"checkout <submodule>" updates recursively' '
+	git update-index --refresh &&
+	git diff-files --quiet &&
+	git diff-index --quiet --cached HEAD &&
+	git checkout HEAD^ submodule &&
+	git diff-files --quiet &&
+	git checkout HEAD submodule &&
+	git diff-files --quiet
+'
+
 test_done

@@ -11,7 +11,7 @@ SYNOPSIS
 [verse]
 'git checkout-index' [-u] [-q] [-a] [-f] [-n] [--prefix=<string>]
 		   [--stage=<number>|all]
-		   [--temp]
+		   [--temp] [--ignore-submodules]
 		   [-z] [--stdin]
 		   [--] [<file>]\*

@@ -68,6 +68,13 @@ OPTIONS
 	Only meaningful with `--stdin`; paths are separated with
 	NUL character instead of LF.

+--ignore-submodules::
+	Since version 1.8.0 the default behavior is to checkout populated
+	submodules recursively. When this option is used, the work trees of
+	submodules will not be updated, only the hash recorded in the
+	superproject will be changed (this was the default behavior until
+	1.8.0).
+
 \--::
 	Do not interpret any more arguments as options.

@@ -213,7 +213,7 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
 	int all = 0;
 	int read_from_stdin = 0;
 	int prefix_length;
-	int force = 0, quiet = 0, not_new = 0;
+	int force = 0, quiet = 0, not_new = 0, ignore_submodules = 0;
 	struct option builtin_checkout_index_options[] = {
 		OPT_BOOLEAN('a', "all", &all,
 			"checks out all files in the index"),

@@ -238,6 +238,8 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
 		OPT_CALLBACK(0, "stage", NULL, NULL,
 			"copy out the files from named stage",
 			option_parse_stage),
+		OPT_BOOLEAN(0, "ignore-submodules", &ignore_submodules,
+			"don't update submodule work trees"),
 		OPT_END()
 	};

@@ -254,7 +256,7 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
 	state.force = force;
 	state.quiet = quiet;
 	state.not_new = not_new;
-	state.ignore_submodules = 1;
+	state.ignore_submodules = ignore_submodules;

 	if (state.base_dir_len || to_tempfile) {
 		/* when --prefix is specified we do not