gitk and git-gui with --git-dir and GIT_DIR

[Michael J Gruber <michaeljgruber+gmane@fastmail.fm>]

I want to track a tree where I should not store a ".git" dir. (You may 
as well assume I don't have direct write access.) So, the ".git" dir is 
somewhere else in the filesystem, actually named something like "repo.git".

I know how to make most of git happy with that structure (even diff). 
Notable exceptions are gitk and git-gui:

gitk::
It requires GIT_DIR to be set and is happy. Only downside is that gitk 
does not fit inside the git-command scheme. Therefore, any aliasing I do 
for git commands does not apply to gitk. Having gitk as git-view or such 
would help.

git-gui::
For non-bare repos it expects git-dirs of the form "path/.git" and bails 
out otherwise. Even when I rename my git dir to such a path things do 
not work: all tracked files are reported missing. This happens even when 
I call git-gui from the actual work tree, i.e. when git diff would work!
It seems as if git-gui is CDing to "path" when git-dir is "path/.git", 
no matter what $PWD, core.worktree or GIT_WORK_TREE say. I don't see why 
this should be desired behaviour.

Michael