git fetch slow as molasses due to tag downloading

Hello,

just upgraded our autobuilder from 1.4.3 to 1.4.4.2.

Now, our standard download command comes to a complete halt. Judging from the "ps -ef" apparently, it does

   git-show-ref --verify --quiet -- [TAG]

This is done for every one of the 1500 tags that are in my repository. At approx 20 tags per second this takes an awful lot of time.

1. Is this necessary? 

2. Is this efficient?  Wouldn't doing all tags in a single git-show-ref
invocation be potentially quicker?