doc index improvements

[marmarek]

Make it produce less white spaces/empty lines and make it work with translated pages.
See individual commits for details.

[andrewdavidwong]

Can we have only one opening/closing operator per line? In other words:

{% for page in all_docs %}
  {% if page.url == sub.url -%}
    <li><a href="{{ sub.url }}">{{ page.title }}</a></li>
  {%- endif  %}
{% endfor %}

[andrewdavidwong]

This is the only thing I want to confirm before merging.

[marmarek]

Done.

[andrewdavidwong]

Mark single-line statements with '-' at the end, to strip blanks after
it - otherwise lines like {% assign ... %} will produce empty line in
the output.
Do the same with 'for' loops and embedded 'if' inside, but be careful to
not strip too much, to still insert newlines between list items (loop
iterations).

Neat trick! I didn't know about it.

This is especially important for loops iterating many times (like,
enumerating the whole site.doc), otherwise the output may be a huge file
of mostly spaces and newlines. With translated repo included, I managed
to get about 800KB doc index file...

Yes, I noticed that too. In general, the best solution (after the improvements you've made here) would be to minify our output. This method sounds like it might be promising, and there are many others discussed on the web.

Furthermore, optimize external doc generation. Specifically - do
not iterate over the whole site.doc for external docs - those won't
match anyway. This saves about 2s of site build time.

Good catch. Thank you!

Also, iterate over subpages/subpages3 once, not twice. This IMO makes
it easier to follow - it's more obvious the entry is either external doc
or not - but not both.

Ok, thank you.