Document an edge case.

diff --git a/comparator.xml b/comparator.xml
index c1d2e5817dde1dcefd9dea7ec93be5e5f1091d4c..ae4ba79c2f4341a9187ef9ac3b5929cac06da385 100644 (file)
--- a/comparator.xml
+++ b/comparator.xml
@@ -304,6 +304,11 @@ almost ridiculously fast on machines with enough core (the author has
 observed speeds of up to two million lines of code compared per minute
 on a 1.8GHz Intel box), but machines with small memories will thrash
 their guts out as the VM subsystem tries to cope.</para>
+
+<para>Comparing a directory to itself will show no similarities.  This
+is because the algorithm ignores matching shreds from within a
+single directory, and it only knows which directory a shred came from
+by relative pathname.</para>
 </refsect1>
 </refentry>