Say I’m writing a journal and want to make sure I’m not leaking names. I’d like to change it consistently so it’s anonymous, but still makes sense.

Instead of this

John force-pushed to `master` for some reason.  Harold didn't pull before he
added his fix and Betty ended up cherry-picking into yet another branch.  To
avoid this, next time we could...

I’d like this

Farmboy force-pushed to `master` for some reason.  Jimmybob didn't pull before
he added his fix and Horsenator ended up cherry-picking into yet another
branch.  To avoid this, next time we could...

Find-and-replace is what I want to do, but consistently and repeatedly (and quickly!). sed is the tool for the job.

First, define the replacements in files named encode and decode.

Encode

s/Betty/Horsenator/g
s/Harold/Jimmybob/g
s/John/Farmboy/g

Decode

s/Horsenator/Betty/g
s/Jimmybob/Harold/g
s/Farmboy/John/g

Replace

Then to replace, we use one of

sed -i "" -f encode journal.md
sed -i "" -f decode journal.md

Obviously, we don’t want to keep the encode/decode files with the output, but you get the idea. You can also send a whole bunch of files through sed with this set up. Maybe you could add a build step that cleans up content or something.

This article gives explains a few more basic sed options that may help you get started.

You can find an example here to play with.