Configure diff-lcs version by Ruby version

Author: JonRowe

Gemfile

@@ -21,7 +21,12 @@ else
   gem 'rake', '>= 12.3.3'
 end
 
-gem 'diff-lcs', ENV.fetch('DIFF_LCS_VERSION', '~> 1.4')
+if RUBY_VERSION.to_f < 2
+  default_diff_lcs_version = '~> 1.3.0'
+else
+  default_diff_lcs_version = '~> 1.4'
+end
+gem 'diff-lcs', ENV.fetch('DIFF_LCS_VERSION', default_diff_lcs_version)
 
 if RUBY_VERSION < '2.2.0' && !!(RbConfig::CONFIG['host_os'] =~ /cygwin|mswin|mingw|bccwin|wince|emx/)
   gem "childprocess", "< 1.0.0"