git-clone: tell the user a bit more about clone-pack failure.

When clone-pack has trouble with the remote, it dies unfriendly
"EOF" error message.  We cannot tell the reason why it failed
from the local end; it could be that the repository did not
exist, or configured not to serve over git-daemon, or a network
failure.  At least, saying clone-pack failed makes it a bit more
meaningful.

I am not convinced yet that removing the newly created directory
is the right thing to do, so this commit leaves the new
directory behind.

Reported by Sam Ravnborg.

Signed-off-by: Junio C Hamano <junkio@cox.net>

git-clone.sh

@@ -188,7 +188,10 @@ yes,yes)
 		cd "$D" && case "$upload_pack" in
 		'') git-clone-pack $quiet "$repo" ;;
 		*) git-clone-pack $quiet "$upload_pack" "$repo" ;;
-		esac
+		esac || {
+			echo >&2 "clone-pack from '$repo' failed."
+			exit 1
+		}
 		;;
 	esac
 	;;