--- debdiff.pl.orig	2006-04-05 19:35:25.000000000 +0200
+++ debdiff.pl	2006-05-31 17:41:25.000000000 +0200
@@ -32,7 +32,8 @@
 
 sub usage {
     print <<"EOF";
-Usage: $progname [option] ... deb1 deb2
+Usage: $progname [option] ...
+   or: $progname [option] ... deb1 deb2
    or: $progname [option] ... changes1 changes2
    or: $progname [option] ... dsc1 dsc2
    or: $progname [option] ... --from deb1a deb1b ... --to deb2a deb2b ...
@@ -234,6 +235,24 @@
     }
 }
 
+my $guessedfiles = 0;
+
+# If no file given, we assume we are in a source directory
+# and try to diff with previous version
+if(@ARGV == 0) {
+    fatal "Can't read file: debian/changelog" unless -r "debian/changelog";
+    open CHL, "debian/changelog";
+    while(<CHL>) {
+	if(/^(.+)\s\((\d+:)?(.+)\)\s(\w+)\;\surgency=.+$/) {
+	    unshift @ARGV, "../".$1."_".$3.".dsc";
+	    $guessedfiles++;
+	}
+	last if $guessedfiles > 1;
+    }
+    close CHL;
+}
+
+
 if (! $type) {
     # we need 2 deb files or changes files to compare
     fatal "Need exactly two deb files or changes files to compare"