connect_work_tree_and_git_dir: safely create leading directories

In a later patch we'll use connect_work_tree_and_git_dir when the
directory for the gitlink file doesn't exist yet. This patch makes
connect_work_tree_and_git_dir safe to use for both cases of
either the git dir or the working dir missing.

To do so, we need to call safe_create_leading_directories[_const]
on both directories. However this has to happen before we construct
the absolute paths as real_pathdup assumes the directories to
be there already.

So for both the config file in the git dir as well as the .git link
file we need to
a) construct the name
b) call SCLD
c) get the absolute path
d) once a-c is done for both we can consume the absolute path
   to compute the relative path to each other and store those
   relative paths.

The implementation provided here puts a) and b) for both cases first,
and then performs c and d after.

One of the two users of 'connect_work_tree_and_git_dir' already checked
for the directory being there, so we can loose that check as
connect_work_tree_and_git_dir handles this functionality now.

Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

dir.c

@@ -2728,23 +2728,33 @@ void untracked_cache_add_to_index(struct index_state *istate,
 /* 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_);
-	char *work_tree = real_pathdup(work_tree_);
+	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_);
+
+	/* 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);

submodule.c

@@ -1445,8 +1445,6 @@ void absorb_git_dir_into_superproject(const char *prefix,
 
 	/* Not populated? */
 	if (!sub_git_dir) {
-		char *real_new_git_dir;
-		const char *new_git_dir;
 		const struct submodule *sub;
 
 		if (err_code == READ_GITFILE_ERR_STAT_FAILED) {
@@ -1469,13 +1467,8 @@ void absorb_git_dir_into_superproject(const char *prefix,
 		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);
-		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);