Call unuse before post-clone hook

Use case:
I manage vim bundles with NeoBundle, so NeoBundle repo should be separately delivered into ~/.vim/bundle folder.
I do not add this repo to my vim vcsh config, I just add post clone hook to do it for me:

`.config/vcsh/hooks-enabled/vim.post-clone`:
```bash
#!/usr/bin/env bash

git clone git://github.com/Shougo/neobundle.vim ~/.vim/bundle/neobundle.vim
```
Without calling `unuse` before post-clone it fails. 
Maybe we really should add one more hook, like `post-clone-cleaned` or `post-clone-after`
And if you find a better name for `unuse` it would be great, because I'm terrible at naming things.

If you know how to solve this problem without post-clone hook, please let me know.