meaning of HEAD in context of filter-branch

I tried to process some files that changed between each commit using the command

git filter-branch --tree-filter 'git diff --name-only HEAD^.. | foo

however it seems that HEAD is fixed to mean the HEAD of the current tip before starting git-filter-branch, by trying like this

$ git rev-list -1 HEAD^ 2bf95faed2d51c338ea6fa93e7bb6cc9c1bc759b

git filter-branch --tree-filter 'git rev-list -1 HEAD^ >>/tmp/sha' -- --all $ cat /tmp/sha 2bf95faed2d51c338ea6fa93e7bb6cc9c1bc759b 2bf95faed2d51c338ea6fa93e7bb6cc9c1bc759b 2bf95faed2d51c338ea6fa93e7bb6cc9c1bc759b 2bf95faed2d51c338ea6fa93e7bb6cc9c1bc759b

how to get the HEAD during filter-branch or other workaround?