hardlink: (man) add note note about ULFILEEQ_DEBUG=

Addresses: https://github.com/util-linux/util-linux/discussions/3323
Signed-off-by: Karel Zak <kzak@redhat.com>
(cherry picked from commit d073aab9d34eea205545c77222947691f4abf5aa)

diff --git a/misc-utils/hardlink.1.adoc b/misc-utils/hardlink.1.adoc
index e09572f6c0f0300ead7ac706954e38c63fba5df2..9cd2b6ddd016a2dcf9b9050b7e2eba05bc0bb004 100644 (file)
--- a/misc-utils/hardlink.1.adoc
+++ b/misc-utils/hardlink.1.adoc
@@ -150,6 +150,11 @@ include::man-common/help-version.adoc[]
 
 *hardlink* takes one or more directories which will be searched for files to be linked.
 
+== ENVIRONMENT
+
+*ULFILEEQ_DEBUG*=all::
+Enables debug output for file comparisons.
+
 == BUGS
 
 The original *hardlink* implementation uses the option *-f* to force hardlinks creation between filesystem. This very rarely usable feature is no more supported by the current *hardlink*.