Hmm...  Looks like a unified diff to me...
The text leading up to this was:
--------------------------
|From 4b6b51100fa14256753f663c93daeb0f89f0a65a Mon Sep 17 00:00:00 2001
|From: Matthias Schoth <mschoth@gmail.com>
|Date: Fri, 15 May 2020 22:10:27 +0200
|Subject: [PATCH] Add key commands that are commonly used in terminal
| applications to slock.
|
|---
| slock.c | 16 ++++++++++++++++
| 1 file changed, 16 insertions(+)
|
|diff --git a/slock.c b/slock.c
|index d2f0886..bf1a392 100644
|--- a/slock.c
|+++ b/slock.c
--------------------------
Patching file slock.c using Plan A...
Hunk #1 succeeded at 156.
Hmm...  Ignoring the trailing garbage.
done