fetch-pack: sort incoming heads list earlier

Commit 4435968 started sorting heads fed to fetch-pack so
that later commits could use more optimized algorithms;
commit 7db8d53 switched the remove_duplicates function to
such an algorithm.

Of course, the sorting is more effective if you do it
_before_ the algorithm in question.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

builtin/fetch-pack.c

@@ -1082,8 +1082,8 @@ struct ref *fetch_pack(struct fetch_pack_args *my_args,
 	}
 
 	if (heads && nr_heads) {
-		nr_heads = remove_duplicates(nr_heads, heads);
 		qsort(heads, nr_heads, sizeof(*heads), compare_heads);
+		nr_heads = remove_duplicates(nr_heads, heads);
 	}
 
 	if (!ref) {