From cb6b76be475c2c7764b7a059175254af734c61af Mon Sep 17 00:00:00 2001
From: Michael Mikonos <127171689+mknos@users.noreply.github.com>
Date: Sat, 2 Dec 2023 22:25:01 +0800
Subject: [PATCH] diff: comparing stdin with directory

* "perl diff . -" and "perl diff - ." are not valid usages because comparing stdin with a directory is no allowed
* Instead of failing in open() with a confusing error, output an error consistent with GNU diff
---
 bin/diff | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/bin/diff b/bin/diff
index d1c7704e..87b913cd 100755
--- a/bin/diff
+++ b/bin/diff
@@ -129,8 +129,10 @@ my ($fh1, $fh2);
 
 if ($file1 eq '-') {
     exit 0 if ($file2 eq '-');
+    bag("cannot compare '-' to a directory") if (-d $file2);
     $fh1 = *STDIN;
 } elsif (-d $file1) {
+    bag("cannot compare '-' to a directory") if ($file2 eq '-');
     bag("'$file2': is a directory") if (-d $file2);
     my $path = join('/', $file1, basename($file2));
     open($fh1, '<', $path) or bag("Couldn't open '$path': $!");