diff --no-index: fix -R with stdin

When -R is given, queue_diff() swaps the mode and name variables of the
two files to produce a reverse diff.  1e3f26542a (diff --no-index:
support reading from named pipes, 2023-07-05) added variables that
indicate whether files are special, i.e named pipes or - for stdin.
These new variables were not swapped, though, which broke the handling
of stdin with with -R.  Swap them like the other metadata variables.

Reported-by: Martin Storsjö <martin@martin.st>
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff-no-index.c

@@ -232,6 +232,7 @@ static int queue_diff(struct diff_options *o,
 		if (o->flags.reverse_diff) {
 			SWAP(mode1, mode2);
 			SWAP(name1, name2);
+			SWAP(special1, special2);
 		}
 
 		d1 = noindex_filespec(name1, mode1, special1);