Feature or a bug: git aliases are executed in git-root directory

Hi,

i started to use git (version is 1.6.3.3 (ubuntu)) and it is really great!

but i have one problem when using aliases. maybe i made a mistake, but here is my problem.

i set up my ~/.gitconfig as follows:
----------
...
[alias]
    meld = !GIT_EXTERNAL_DIFF='git-diff-to-meld-redirect' git diff
...
----------

now when i work in a subdirectory of my git-root dir and want to make a diff, this works perfectly: $ cd ~/git-root/subdir $ git diff some_file

but when doing the same using the alias i get an error: $ cd ~/git-root/subdir $ git meld some_file fatal: ambiguous argument 'some_file': unknown revision or path not in the working tree. Use '--' to separate paths from revisions

whereas using the relative path starting from the git-root directory works $ cd ~/git-root/subdir $ git meld subdir/some_file

is there a way to solve this problem?

thanks for your help jens