Merge branch 'maint-1.6.6' into maint

* maint-1.6.6:
  dwim_ref: fix dangling symref warning
  stash pop: remove 'apply' options during 'drop' invocation
  diff: make sure --output=/bad/path is caught
  Remove hyphen from "git-command" in two error messages

diff.c

@@ -2893,6 +2893,8 @@ int diff_opt_parse(struct diff_options *options, const char **av, int ac)
 		;
 	else if (!prefixcmp(arg, "--output=")) {
 		options->file = fopen(arg + strlen("--output="), "w");
+		if (!options->file)
+			die_errno("Could not open '%s'", arg + strlen("--output="));
 		options->close_file = 1;
 	} else
 		return 0;