github-cheat-sheet VS bfg-repo-cleaner

Not aware of a book - but what you describe sounds a little like the github cheatsheet - could it be someone turned this (or the talk mentioned in the intro) into an ebook or pdf?

GitHub Cheat Sheet - Tim Green (Markdown)

So, this is a PSA that you can't simply delete the file and commit that. You must either use a tool like BFG Repo Cleaner which can scrub files out of your commit history or you could simply delete your repository and recreate it (easier, but you lose your commit history).

It shouldn't take a lot of time to modify. There is even a tool just for this scenario https://rtyley.github.io/bfg-repo-cleaner/

You need to git out the BFG: https://rtyley.github.io/bfg-repo-cleaner/

This method requires changes to be committed as usual in the regular project repository, and then committed again in the -docs repository. This is inelegant, but it provides clear distinction between private and public content. You cannot publish your regular repository without using git-filter-branch or some Git history rewriting software like BFG Repo-Cleaner. This would rewrite every commit in the history of the repo, removing all changes to the paths you don't wish to publish. This would change all the commit hashes and possibly other metadata – in short, it wouldn't be the same repository.

GFG Repo-Cleaner

You could use a repo filtering tool (e.g. BFG Repo-Cleaner) to clean up unintended information leak from your Git repository -- which retains the history timeline, but I believe it would rehash all the commits and render everything unsigned, which is probably not the desired outcome.