"SHA256ify" commits

[Darren Pilgrim]

There's no criticism here, just one geek's interested query.  I'm already
familiar with the reasons for moving to SHA256, but how is this process
being accomplished?  What are you using to calculate and insert the new
hashes?  What conditions result in the "manually checked and updated"
commit?  If there's previous list traffic answering these questions, by all
means, point me in a direction.