- hosts: all
  tasks:

  - name: install fish
    package:
      name: fish
      state: present

  - name: find where fish is
    command: which fish
    register: which_fish

  - name: add fish to /etc/shells
    lineinfile: dest=/etc/shells line={{ which_fish.stdout | trim }} state=present
    become: yes

  - name: set the default user shell to fish
    user: name={{ ansible_env.USER }} shell={{ which_fish.stdout | trim }}
    become: yes