Stop tracking a file in git - without having it deleted either locally or on pull

I want to ignore a file/directory tree that was previously tracked - ignore it forever but have it not being deleted on a pull - just have it ignored on the repository the pull happened. Is this possible ? Why not (if not) ? How should I proceed ?

NB: the accepted answer in Remove a file from a Git repository without deleting it from the local filesystem - namely git rm --cached path - will result in the file being deleted on a pull. Nasty. Not only that but "it will delete your file if you check out a revision from before the deletion and then check out a revision from after the deletion" (see this comment) See this question for other interesting comments/answers that do not address my issue however.

I am perfectly aware of the --assume-unchanged flag but this is not what I want - I want to tell to git (and all repository clones) "hey, stop tracking this file/tree" but not "delete this file/tree" - so I want to --assume-unchanged globally as it were. If it is not possible (why ?) I need a workaround.

For the record I am trying to bootstrap git to use it to keep/share history and I want to be able to stop tracking files/directories at will - without having them deleted.

git assume-unchanged vs skip-worktree - the general advice for assume-unchanged should be taken with a grain of salt (on pull, reset --hard etc)
git assume unchanged vs skip worktree - ignoring a symbolic link - see this answer for core.sparseCheckout

Solution

This is not possible. To prevent new changes from being tracked, you need to remove the file from the repository (using git rm or git rm --cached). This adds a change to the commit that removes the file. When that change is then applied in other repositories, the remove action is performed, resulting in the file being removed.