file.append example

defaults.sls

/etc/xdg/mimeapps.list:
    file.absent
default_applications:
    file.append:
        - name: /etc/xdg/mimeapps.list
        - text: |
            [Default Applications]
        
{% for mimetype in pillar['default_applications'] %}
{{ mimetype }}:
    file.append:
        - name: /etc/xdg/mimeapps.list
        - text: 
            - {{ mimetype }}=
{% for desktop in pillar['default_applications'][mimetype] %}
{{ mimetype }}_{{ desktop }}:
    file.append:
        - name: /etc/xdg/mimeapps.list
        - text: 
            - {{ desktop }};
{% endfor %}
append_newline_{{ mimetype }}:
    file.append:
        - name: /etc/xdg/mimeapps.list
        - text:
            - \n
{% endfor %}

mimeapps.sls

default_applications:
  inode/directory:
    - pcmanfm-qt.desktop
  text/html:
    - google-chrome.desktop
  x-scheme-handler/http:
    - google-chrome.desktop
  x-scheme-handler/https:
    - google-chrome.desktop