[PATCH] doc: The test "==" operator is a GNU extension.

[Ben Pfaff]

* doc/coreutils.texi (test invocation): Mark the "==" operator as a GNU
extension, to reduce the number of people who accidentally use it while
thinking it's portable.
---
 doc/coreutils.texi | 1 +
 1 file changed, 1 insertion(+)

diff --git a/doc/coreutils.texi b/doc/coreutils.texi
index 8d9320ca2..601b06300 100644
--- a/doc/coreutils.texi
+++ b/doc/coreutils.texi
@@ -13336,6 +13336,7 @@ True if the strings are equal.
 @opindex ==
 @cindex equal string check
 True if the strings are equal (synonym for =).
+This form is a GNU extension.
 
 @item @var{string1} != @var{string2}
 @opindex !=
-- 
2.28.0