/usr/lib/ruby/vendor_ruby/active_support/core_ext/array/prepend_and_append.rb is in ruby-activesupport-3.2 3.2.16-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 | class Array
# The human way of thinking about adding stuff to the end of a list is with append
alias_method :append, :<<
# The human way of thinking about adding stuff to the beginning of a list is with prepend
alias_method :prepend, :unshift
end
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