form タグのフォーマット仕様

It always takes at least one argument, but we don't break it
printWidth: 1
{% form x %}{% endform %}
{% form x %}
  hello
{% endform %}

It can take named arguments, and respects liquidSingleQuote
printWidth: 1
{% form 'cart',
  key: value
%}{% endform %}

It can take named arguments, and respects liquidSingleQuote (pw80)
printWidth: 80
{% form 'cart', key1: value1, key2: 'value2' %}{% endform %}

It can take positional arguments
printWidth: 1
{% form 'cart',
  pos1
%}{% endform %}
{% form 'cart',
  pos1,
  pos2
%}{% endform %}

It can take positional and named arguments (at the same time)
printWidth: 1
{% form 'cart',
  pos1[0],
  empty,
  key: true,
  ind: (0..2)
%}
  <input type="submit">
{% endform %}

It indents content (without whitespace stripping b/c form is inner insensitive)
printWidth: 1
{% form 'cart',
  pos1
%}
  hello
{% endform %}