Hello,
Work to arrive at one patch (e.g. [1]) is many times non-trivial, even if the patch is.
Part of the work is explained in the commit message, but only a tiny amount.
For a full explanation of the removal of GNU_ROFF I wrote a blog post with much more detail:
https://felipec.wordpress.com/2021/06/05/adventures-with-man-color/
Cheers.
[1] https://lore.kernel.org/git/20210515115653.922902-2-felipe.contreras@gmail.com/
-- Felipe Contreras