git-pack-objects: make "--window=x" semantics more logical.

A zero disables delta generation (like before), but we make the window
be one bigger than specified, since we use one entry for the one to be
tested (it used to be that "--window=1" was meaningless, since we'd have
used up the single-entry window with the entry to be tested, and had no
chance of actually ever finding a delta).

The default window remains at 10, but now it really means "test the 10
closest objects", not "test the 9 closest objects".

pack-objects.c

@@ -26,7 +26,6 @@ struct object_entry {
 static struct object_entry **sorted_by_sha, **sorted_by_type;
 static struct object_entry *objects = NULL;
 static int nr_objects = 0, nr_alloc = 0;
-static int delta_window = 10;
 static const char *base_name;
 
 struct myfile {
@@ -364,6 +363,7 @@ static void find_deltas(struct object_entry **list, int window)
 int main(int argc, char **argv)
 {
 	char line[128];
+	int window = 10;
 	int i;
 
 	for (i = 1; i < argc; i++) {
@@ -372,7 +372,7 @@ int main(int argc, char **argv)
 		if (*arg == '-') {
 			if (!strncmp("--window=", arg, 9)) {
 				char *end;
-				delta_window = strtoul(arg+9, &end, 0);
+				window = strtoul(arg+9, &end, 0);
 				if (!arg[9] || *end)
 					usage(pack_usage);
 				continue;
@@ -399,8 +399,8 @@ int main(int argc, char **argv)
 
 	sorted_by_sha = create_sorted_list(sha1_sort);
 	sorted_by_type = create_sorted_list(type_size_sort);
-	if (delta_window)
+	if (window)
-		find_deltas(sorted_by_type, delta_window);
+		find_deltas(sorted_by_type, window+1);
 
 	write_pack_file();
 	write_index_file();