Index: Makefile.in
--- Makefile.in.orig	2015-04-20 21:29:45.000000000 +0200
+++ Makefile.in	2015-08-05 22:57:50.383267669 +0200
@@ -517,7 +517,7 @@
 	scripts/recountdiff \
 	scripts/unwrapdiff \
 	scripts/dehtmldiff \
-	scripts/espdiff
+	scripts/espdiff scripts/gendiff
 
 AM_CFLAGS = -I$(srcdir)/src
 src_interdiff_SOURCES = src/interdiff.c src/util.c src/util.h src/diff.c \
@@ -771,6 +771,8 @@
 	cd $(top_builddir) && $(SHELL) ./config.status $@
 scripts/espdiff: $(top_builddir)/config.status $(top_srcdir)/scripts/espdiff.in
 	cd $(top_builddir) && $(SHELL) ./config.status $@
+scripts/gendiff: $(top_builddir)/config.status $(top_srcdir)/scripts/gendiff.in
+	cd $(top_builddir) && $(SHELL) ./config.status $@
 patchutils.spec: $(top_builddir)/config.status $(srcdir)/patchutils.spec.in
 	cd $(top_builddir) && $(SHELL) ./config.status $@
 install-binPROGRAMS: $(bin_PROGRAMS)
Index: configure
--- configure.orig	2015-08-05 22:56:28.104281000 +0200
+++ configure	2015-08-05 22:56:42.283207606 +0200
@@ -5027,7 +5027,7 @@
 _ACEOF
 
 
-ac_config_files="$ac_config_files Makefile scripts/splitdiff scripts/editdiff scripts/fixcvsdiff scripts/recountdiff scripts/unwrapdiff scripts/dehtmldiff scripts/espdiff patchutils.spec"
+ac_config_files="$ac_config_files Makefile scripts/splitdiff scripts/editdiff scripts/fixcvsdiff scripts/recountdiff scripts/unwrapdiff scripts/dehtmldiff scripts/espdiff patchutils.spec scripts/gendiff"
 
 cat >confcache <<\_ACEOF
 # This file is a shell script that caches the results of configure
Index: scripts/gendiff.in
--- scripts/gendiff.in.orig	2015-08-05 22:56:28.113091362 +0200
+++ scripts/gendiff.in	2015-08-05 22:56:28.113091362 +0200
@@ -0,0 +1,18 @@
+#!/bin/bash
+if [ $# -ne 2 ]; then
+    echo "Usage: ${0##*/} DIRECTORY DIFF-SUFFIX" 1>&2
+    exit 1
+fi
+find "$1" \( -name "*$2" -o -name ".*$2" \) -print |\
+while read OP; do
+    NP="${OP%$2}"
+    NN="${NP##*/}"
+    U="-u"
+    if [ "$NN" = "ChangeLog" ]; then
+        U="-U0"
+    fi
+    case "${NN##*.}" in
+        c|cc|C|cpp) U="$U -p" ;;
+    esac
+    diff $U "$OP" "$NP"
+done