[PATCH 09/16] entry.c: optionally checkout submodules

@@ -1,5 +1,6 @@
 #include "cache.h"
 #include "blob.h"
+#include "run-command.h"
 
 static void create_directories(const char *path, const struct checkout *state)
 {

@@ -163,6 +164,44 @@ static int write_entry(struct cache_entry *ce, char *path, const struct checkout
 	return 0;
 }
 
+static int checkout_submodule(const char *path, struct cache_entry *ce, const struct checkout *state)
+{
+	static char cwd[PATH_MAX];
+	const char *gitdirenv;
+	const char *args[10];
+	int argc;
+	int err;
+
+	if (!state->submodules)
+		return 0;
+
+	if (!getcwd(cwd, sizeof(cwd)) || cwd[0] != '/')
+		die("Unable to read current working directory");
+
+	if (chdir(path))
+		die("Cannot move to '%s'", path);
+
+	argc = 0;
+	args[argc++] = "checkout";
+	if (state->force)
+	    args[argc++] = "-f";
+	args[argc++] = sha1_to_hex(ce->sha1);
+	args[argc] = NULL;
+
+	gitdirenv = getenv(GIT_DIR_ENVIRONMENT);
+	unsetenv(GIT_DIR_ENVIRONMENT);
+	err = run_command_v_opt(args, RUN_GIT_CMD);
+	setenv(GIT_DIR_ENVIRONMENT, gitdirenv, 1);
+
+	if (chdir(cwd))
+		die("Cannot come back to cwd");
+
+	if (err)
+		return error("failed to run git-checkout in submodule '%s'", path);
+
+	return 0;
+}
+
 int checkout_entry(struct cache_entry *ce, const struct checkout *state, char *topath)
 {
 	static char path[PATH_MAX + 1];

@@ -193,9 +232,8 @@ int checkout_entry(struct cache_entry *ce, const struct checkout *state, char *t
 		 */
 		unlink(path);
 		if (S_ISDIR(st.st_mode)) {
-			/* If it is a gitlink, leave it alone! */
 			if (S_ISDIRLNK(ntohl(ce->ce_mode)))
-				return 0;
+				return checkout_submodule(path, ce, state);
 			if (!state->force)
 				return error("%s is a directory", path);
 			remove_subtree(path);