[BUG] Git 1.6.6 can't clone tags after filter-branch

Hi,

This series of commands:

  git init
  touch file1
  git add file1
  git commit -m 1
  echo >> file1
  touch file2
  git add file1 file2
  git commit -m 2
  git tag -m 'mytag' mytag
  git filter-branch --index-filter 'git rm --cached --ignore-unmatch file2' \
    --tag-name-filter cat -f -- --all
  git clone file://$PWD temp

Results in an error from the clone command:

  error: refs/tags/mytag does not point to a valid object!

The clone command exits with zero status, but the new repo doesn't contain the tag 'mytag'.

Version 1.6.2.5 did not have this problem.  It bisects to:

  commit 5bdc32d3e50d8335c65e136e6b5234c5dd92a7a9
  Author: Nicolas Pitre <nico@fluxnic.net>
  Date:   Fri Sep 25 23:54:42 2009 -0400

      make 'git clone' ask the remote only for objects it cares about

James