Why is "Sparse checkout leaves no entry on working directory" fatal?

Hello,

I am trying to add a file to an arbitrary branch without touching the current worktree with as little overhead as possible.

For this, the sparse-checkout feature in conjuntion with the "shared repository" feature seems to be perfect.

The basic idea goes like this:

   TMP=`mktemp -d /var/tmp/test-XXXXXXXXX`
   GD=$TMP/git
   WD=$TMP/wd
   
   git --work-tree $WD --git-dir $GD clone -qns -n . $GD
   git --work-tree $WD --git-dir $GD config core.sparsecheckout true
   echo path/of/file/which/I/want/to/create >>$GD/info/sparse-checkout
   
   git --work-tree $WD --git-dir $GD checkout -b some-branch remotes/origin/some-branch  # !!!
   
   ( cd $WD
     mkdir -p path/of/file/which/I/want/to
     echo huhuh >path/of/file/which/I/want/to/create
     git --work-tree $WD --git-dir $GD add path/of/file/which/I/want/to/create
     git --work-tree $WD --git-dir $GD commit
     git --work-tree $WD --git-dir $GD push
   )
   
   rm -rf $TMP

Unfortunately, the marked command errors out with

   "error: Sparse checkout leaves no entry on working directory"

and won't create/switch to the branch that is to be modified.

Strange enough, I have some repositories at this machine where the .git/info/sparse-checkout file contains only non-existing files and git happily executes this "git checkout -b XXX remotes/origin/XXX" command leaving the working tree totally empty all the time.

Someone understands this inconsistent behaviour?