init: Do not segfault on big GIT_TEMPLATE_DIR environment variable

Signed-off-by: NFrank Lichtenheld <flichtenheld@astaro.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

builtin-init-db.c

@@ -122,8 +122,10 @@ static void copy_templates(const char *template_dir)
 		template_dir = system_path(DEFAULT_GIT_TEMPLATE_DIR);
 	if (!template_dir[0])
 		return;
+	template_len = strlen(template_dir);
+	if (PATH_MAX <= (template_len+strlen("/config")))
+		die("insanely long template path %s", template_dir);
 	strcpy(template_path, template_dir);
-	template_len = strlen(template_path);
 	if (template_path[template_len-1] != '/') {
 		template_path[template_len++] = '/';
 		template_path[template_len] = 0;

t/t0001-init.sh

@@ -199,4 +199,13 @@ test_expect_success 'init honors global core.sharedRepository' '
 	x`git config -f shared-honor-global/.git/config core.sharedRepository`
 '
 
+test_expect_success 'init rejects insanely long --template' '
+	(
+		insane=$(printf "x%09999dx" 1) &&
+		mkdir test &&
+		cd test &&
+		test_must_fail git init --template=$insane
+	)
+'
+
 test_done