move connect_work_tree_and_git_dir to dir.h

That function was primarily used by submodule code, but the function
itself is not inherently about submodules. In the next patch we'll
introduce relocate_git_dir, which can be used by worktrees as well,
so find a neutral middle ground in dir.h.

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

dir.c

@@ -2748,3 +2748,28 @@ void untracked_cache_add_to_index(struct index_state *istate,
 {
 	untracked_cache_invalidate_path(istate, path);
 }
+
+/* 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 rel_path = STRBUF_INIT;
+	char *git_dir = xstrdup(real_path(git_dir_));
+	char *work_tree = xstrdup(real_path(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));
+
+	/* 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",
+			       relative_path(work_tree, git_dir, &rel_path));
+
+	strbuf_release(&file_name);
+	strbuf_release(&rel_path);
+	free(work_tree);
+	free(git_dir);
+}

dir.h

@@ -335,4 +335,5 @@ struct untracked_cache *read_untracked_extension(const void *data, unsigned long
 void write_untracked_extension(struct strbuf *out, struct untracked_cache *untracked);
 void add_untracked_cache(struct index_state *istate);
 void remove_untracked_cache(struct index_state *istate);
+extern void connect_work_tree_and_git_dir(const char *work_tree, const char *git_dir);
 #endif

submodule.c

@@ -1222,31 +1222,6 @@ int merge_submodule(unsigned char result[20], const char *path,
 	return 0;
 }
 
-/* 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 rel_path = STRBUF_INIT;
-	char *git_dir = xstrdup(real_path(git_dir_));
-	char *work_tree = xstrdup(real_path(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));
-
-	/* 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",
-			       relative_path(work_tree, git_dir, &rel_path));
-
-	strbuf_release(&file_name);
-	strbuf_release(&rel_path);
-	free(work_tree);
-	free(git_dir);
-}
-
 int parallel_submodules(void)
 {
 	return parallel_jobs;

submodule.h

@@ -65,7 +65,6 @@ int merge_submodule(unsigned char result[20], const char *path, const unsigned c
 int find_unpushed_submodules(unsigned char new_sha1[20], const char *remotes_name,
 		struct string_list *needs_pushing);
 int push_unpushed_submodules(unsigned char new_sha1[20], const char *remotes_name);
-void connect_work_tree_and_git_dir(const char *work_tree, const char *git_dir);
 int parallel_submodules(void);
 
 /*