Hmm...  Looks like a unified diff to me...
The text leading up to this was:
--------------------------
|diff -up a/slock.c b/slock.c
|--- a/slock.c	2022-10-04 19:45:59.000000000 +0200
|+++ b/slock.c	2024-01-27 22:36:28.398501798 +0100
--------------------------
Patching file slock.c using Plan A...
No such line 164 in input file, ignoring
Hunk #1 failed at 165.
1 out of 1 hunks failed
done