Unwanted directory creation/invitations sent when using the filesystem from fish shell

I recently started using keybase and I noticed a strange behavior when accessing the filesystem. I use the [fish shell](https://github.com/fish-shell/fish-shell), when you type a path it tries to check if it really exist or not and highlights it. So for example if you try to type/paste this path in the shell:

```
/keybase/private/siavashs,someone@twitter/
```

and then try to edit the username, it will result in creation of these directories:

```
siavashs,someo@twitter
siavashs,someon@twitter
siavashs,someone@twitter
...
```

And the worse part is that keybase sent an invitation to all those false usernames.
Being a shell user my expectation is that a filesystem will be modified only when I execute a command.
For example:

``` bash
mkdir /keybase/private/siavashs,someone@twitter/ # Create directories manually
echo "My msg!" > /keybase/private/siavashs,someone@twitter/secret.txt # Only send an invitation when a file is created
```

Reproduce the behavior from fish shell by editing a path under /keybase/private and observe whether partial usernames create directories or send invitations. The issue is resolved when merely typing or editing the path causes no filesystem changes or invitations, while the shown mkdir and file-creation commands retain their intended behavior.

Written by the indexing model from the issue text.