Remove end of file newline from twig files automatically.

Problem/Motivation

For git coding standards all files need an ending blank newline character.
This becomes problematic when it makes twig files add a newline character that may break markup or the tests for the markup.

A workaround that has been used to add a {% spaceless %}...{% endspaceless %} control to solve the problem but that removes spaces from inside as well. The reason spaceless control works is because it is a twig template tag and from Twig docs all template tags remove the proceeding newline character. @see http://twig.sensiolabs.org/doc/templates.html#whitespace-control

Therefore some other solutions were to append a comment to the end of the last HTML line.

</div>{# This comment removes the newline that follows #}

Proposed resolution

We'd like to automatically remove the last newline of the twig files.

For performance reasons Fabian suggests injecting a comment control before the last newline while the twig template is loaded and compiled. We could also possibly do a regex (if it's not too slow) to remove the extra newline character.

Caveat: We don't want to punish themers by removing the newline they intentionally put in.

Remaining tasks

Create a patch along these lines: except from Google Hangouts (Sept 5, 2013)

source = $this->loader->getSource($name);
// Check last character and remove ...
source = $this->loader->getSource($name);

$compiled_source = $this->compileSource($source, $name);
in TwigTemplate::updateCompiledTemplate

$source = $this->loader->getSource($name);
// Check last character and remove ...
And thats it.
to remove the new lines
core/lib/Drupal/Core/Template/TwigEnvironment.php

User interface changes

N/A

API changes

N/A

Related Issues

#1757550: [Meta] Convert core theme functions to Twig templates.