From 810ccab884fb0a2cabaa94d0b1183ed2021a5774 Mon Sep 17 00:00:00 2001
From: Sven van Heugten <sven@memcmp.org>
Date: Thu, 5 Mar 2026 20:53:47 +0100
Subject: [PATCH] Show what happens for a diff with only a mode change

---
 test/mechanicaldiff.bats | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/test/mechanicaldiff.bats b/test/mechanicaldiff.bats
index a0a1e75..6a20d94 100755
--- a/test/mechanicaldiff.bats
+++ b/test/mechanicaldiff.bats
@@ -30,6 +30,20 @@ setup() {
   assert_output ""
 }
 
+@test "keeps diff with only mode change" {
+  printf "%s\n" "foo" >"$BATS_TEST_TMPDIR/old"
+  printf "%s\n" "foo" >"$BATS_TEST_TMPDIR/new"
+  chmod 0644 "$BATS_TEST_TMPDIR/old"
+  chmod 0755 "$BATS_TEST_TMPDIR/new"
+
+  diff_output="$(git diff --no-index "$BATS_TEST_TMPDIR/old" \
+    "$BATS_TEST_TMPDIR/new" || true)"
+
+  run mechanicaldiff.py foo bar <<<"$diff_output"
+  assert_success
+  assert_output "$diff_output"
+}
+
 @test "drops one hunk and keeps another" {
   cat >"$BATS_TEST_TMPDIR/old" <<-'EOF'
 	alpha