When it doesn't break, it should conditionally omit a leading space

It should omit the leading space if it is stripped anyway
{% if A %}{% else -%}space{% endif %}
{% if A %}X{% else -%}space{% endif %}

It should not omit the leading space if there's space before the named branch
(else)
{% if A %}{% else %} space{% endif %}
{% if A %} {% else %} space{% endif %}
{% if A %}X{% else %} space{% endif %}

It should not omit the leading space if there's space before the named branch
(elsif)
{% if A %}{% elsif b %}{% else %} space{% endif %}
{% if A %}{% elsif b %}X{% else %} space{% endif %}
{% if A %}{% elsif b %} {% else %} space{% endif %}
{% if A %}{% elsif b %}X {% else %} space{% endif %}
{% if A %}{% elsif b %} X {% else %} space{% endif %}

It should not omit the whitespace if it is included inline in a paragraph
<p>
  haha{% if A %}{% else %} space{% endif %}
</p>