git-fetch-pack: close output fd after dup'ing the input

With the socket case, the input and output fd's might end up being the same,
so we want to dup the other before we close either of them.

fetch-pack.c

@@ -95,9 +95,9 @@ static int fetch_pack(int fd[2], int nr_match, char **match)
 	if (pid < 0)
 		die("git-fetch-pack: unable to fork off git-unpack-objects");
 	if (!pid) {
-		close(fd[1]);
 		dup2(fd[0], 0);
 		close(fd[0]);
+		close(fd[1]);
 		execlp("git-unpack-objects", "git-unpack-objects", NULL);
 		die("git-unpack-objects exec failed");
 	}