Diff::LCS computes the difference between two Enumerable sequences
https://github.com/halostatue/diff-lcs

Diff::LCS computes the difference between two Enumerable sequences using the
McIlroy-Hunt longest common subsequence (LCS) algorithm. It includes utilities
to create a simple HTML diff output format and a standard diff-like tool.
This is release 1.3, providing a tentative fix to a long-standing issue
related
to incorrect detection of a patch direction. Also modernizes the gem
infrastructure, testing infrastructure, and provides a warning-free experience
to Ruby 2.4 users.