SF# 522426, add doc for common parameter for filecmp.cmpfiles()
diff --git a/Doc/lib/libfilecmp.tex b/Doc/lib/libfilecmp.tex
index c53fc33..6e474ae 100644
--- a/Doc/lib/libfilecmp.tex
+++ b/Doc/lib/libfilecmp.tex
@@ -41,6 +41,7 @@
lack permission to read them or many other reasons, but always that
the comparison could not be done for some reason.
+The \var{common} parameter is a list of file names found in both directories.
The \var{shallow} and \var{use_statcache} parameters have the same
meanings and default values as for \function{filecmp.cmp()}.
\end{funcdesc}