use xgetcwd() to set $GIT_DIR

Instead of dying of a segmentation fault if getcwd() returns NULL, use
xgetcwd() to make sure to write a useful error message and then exit
in an orderly fashion.

Suggested-by: Jeff King <peff@peff.net>
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/init-db.c

@@ -537,10 +537,9 @@ int cmd_init_db(int argc, const char **argv, const char *prefix)
 		usage(init_db_usage[0]);
 	}
 	if (is_bare_repository_cfg == 1) {
-		static char git_dir[PATH_MAX+1];
-
-		setenv(GIT_DIR_ENVIRONMENT,
-			getcwd(git_dir, sizeof(git_dir)), argc > 0);
+		char *cwd = xgetcwd();
+		setenv(GIT_DIR_ENVIRONMENT, cwd, argc > 0);
+		free(cwd);
 	}
 
 	if (init_shared_repository != -1)

git.c

@@ -125,9 +125,10 @@ static int handle_options(const char ***argv, int *argc, int *envchanged)
 			if (envchanged)
 				*envchanged = 1;
 		} else if (!strcmp(cmd, "--bare")) {
-			static char git_dir[PATH_MAX+1];
+			char *cwd = xgetcwd();
 			is_bare_repository_cfg = 1;
-			setenv(GIT_DIR_ENVIRONMENT, getcwd(git_dir, sizeof(git_dir)), 0);
+			setenv(GIT_DIR_ENVIRONMENT, cwd, 0);
+			free(cwd);
 			setenv(GIT_IMPLICIT_WORK_TREE_ENVIRONMENT, "0", 1);
 			if (envchanged)
 				*envchanged = 1;