From 297a9b4b79e76751cf4a1cfc3c333995073b37a8 Mon Sep 17 00:00:00 2001
From: Rob Landley <rob@landley.net>
Date: Tue, 19 Jul 2022 07:37:59 -0500
Subject: [PATCH] Fix off by one error and add test case.

---
 tests/diff.test     | 6 ++++++
 toys/pending/diff.c | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/tests/diff.test b/tests/diff.test
index 8a1f99f4..bbef9d32 100644
--- a/tests/diff.test
+++ b/tests/diff.test
@@ -54,3 +54,9 @@ testcmd "fifos" "-u -L fifo1 -L fifo2 fifo1 fifo2" '--- fifo1
 -2
 +3
 ' "" ""
+
+seq 1 100000 > one
+seq 1 4 100000 > two
+testcmd 'big hunk' '-u --label nope --label nope one two' \
+  "$(echo -e '--- nope\n+++ nope\n@@ -1,100000 +1,25000 @@'; for((i=1;i<=100000;i++)); do (((i-1)&3)) && echo "-$i" || echo " $i"; done)\n" '' ''
+rm one two
diff --git a/toys/pending/diff.c b/toys/pending/diff.c
index 6d63bd59..0ea8fc39 100644
--- a/toys/pending/diff.c
+++ b/toys/pending/diff.c
@@ -529,7 +529,7 @@ char *quote_filename(char *filename)
       if (quote) t[len++] = '"';
       t[len] = 0;
 
-      return --t;
+      return t-quote;
     }
 
     // construct the new string
-- 
2.39.2