enhance clone and fetch -k experience

Now that index-pack can be streamed with a pack, it is probably a good
idea to use it directly instead of creating a temporary file and running
index-pack afterwards.  This way index-pack can abort early whenever a
corruption is encountered even if the pack has not been fully
downloaded, it can display a progress percentage as it knows how much to
expects, and it is a bit faster since the pack indexing is partially
done as data is received. Using fetch -k doesn't need to disable thin
pack generation on the remote end either.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

fetch-pack.c

@@ -518,8 +518,6 @@ int main(int argc, char **argv)
 	}
 	if (!dest)
 		usage(fetch_pack_usage);
-	if (keep_pack)
-		use_thin_pack = 0;
 	pid = git_connect(fd, dest, exec);
 	if (pid < 0)
 		return 1;