Another example from Hunt and McIlroy,
“An Algorithm for Differential File Comparison.”
https://www.cs.dartmouth.edu/~doug/diff.pdf

Anchored diff gives up on finding anything,
since there are no unique lines.

-- old --
a
b
c
a
b
b
a
-- new --
c
a
b
a
b
c
-- diff --
diff old new
--- old
+++ new
@@ -1,7 +1,6 @@
-a
-b
-c
-a
-b
-b
-a
+c
+a
+b
+a
+b
+c
