Use <<~ heredoc where applicable

Author: jirutka

asciidoctor-include-ext.gemspec

@@ -9,13 +9,13 @@ Gem::Specification.new do |s|
   s.license     = 'MIT'
 
   s.summary     = "Asciidoctor's standard include::[] processor reimplemented as an extension"
-  s.description = <<EOF
-This is a reimplementation of the Asciidoctor's built-in (pre)processor for the
-include::[] directive in extensible and more clean way. It provides the same
-features, but you can easily adjust it or extend for your needs. For example,
-you can change how it loads included files or add another ways how to select
-portions of the document to include.
-EOF
+  s.description = <<~EOF
+    This is a reimplementation of the Asciidoctor's built-in (pre)processor for the
+    include::[] directive in extensible and more clean way. It provides the same
+    features, but you can easily adjust it or extend for your needs. For example,
+    you can change how it loads included files or add another ways how to select
+    portions of the document to include.
+  EOF
 
   s.files       = Dir['lib/**/*', '*.gemspec', 'LICENSE*', 'README*']
 

spec/integration_spec.rb

@@ -1,12 +1,9 @@
 require_relative 'spec_helper'
 require 'asciidoctor/include_ext/include_processor'
-require 'corefines'
 require 'webrick'
 
 FIXTURES_DIR = File.expand_path('../fixtures', __FILE__)
 
-using Corefines::String::unindent
-
 describe 'Integration tests' do
 
   subject(:output) { Asciidoctor.convert(input, options) }
@@ -59,7 +56,7 @@
     end
 
     it 'is replaced by a warning when target is not found' do
-      given <<-ADOC.unindent
+      given <<~ADOC
         include::no-such-file.adoc[]
 
         trailing content
@@ -70,7 +67,7 @@
     end
 
     it 'is skipped when target is not found and optional option is set' do
-      given <<-ADOC.unindent
+      given <<~ADOC
         include::no-such-file.adoc[opts=optional]
 
         trailing content
@@ -131,7 +128,7 @@
     end
 
     it 'supports tagged selection in language that uses circumfix comments' do
-      given <<-ADOC.unindent
+      given <<~ADOC
         [source, ml]
         ----
         include::include-file.ml[tag=snippet]