advent_of_code VS git-filter-repo

Caution: the method I used is not recommended. Use at your own risk, know what you're doing, and have plenty of backups, etc. That said, here are my notes.

Once I figured out how to elegantly move the tail using signum() in part 2 it became so much cleaner. Full code is on GitHub, but here's the core of it:

Group the fish by their timer, which can be anything from 0 to 8. The neat part is the rotate_left to decrease the timers of each group. Fish with timer 0 will automatically end up at timer 8, and so the only thing left to do is adding another copy with timer 6. Core function: rust fn multiply(timers: Vec, generations: usize) -> usize { // Index equals timer value, so index 0 contains the count of fish with timer 0 let mut counts_by_timer = vec![0usize; 9]; timers.into_iter().for_each(|f| { counts_by_timer[f] += 1; }); for _ in 0..generations { // A left rotation represents the timer (=index) decreasing by 1. // The fish with timer 0 will not only produce new fish with timer 8, // but also reset their timer to 6 let count_of_fish_with_timer_0 = counts_by_timer[0]; counts_by_timer.rotate_left(1); counts_by_timer[6] += count_of_fish_with_timer_0; // == counts_by_timer[8] } counts_by_timer.into_iter().sum() } Full code at Github

**WARNING**: git-filter-branch has a glut of gotchas generating mangled history rewrites. Hit Ctrl-C before proceeding to abort, then use an alternative filtering tool such as 'git filter-repo' (https://github.com/newren/git-filter-repo/) instead. See the filter-branch manual page for more details; to squelch this warning, set FILTER_BRANCH_SQUELCH_WARNING=1. Proceeding with filter-branch... Rewrite a3a48b09e282854c80bf4ad02a017e249e161fd8 (2/8) (0 seconds passed, remaining 0 predicted) rm 'config.js' Rewrite 6e788e83a338e45b348d93d682b32c816ee2fbff (3/8) (0 seconds passed, remaining 0 predicted) rm 'config.js' Rewrite 7a378a0145bce70bea213ca5f9062138544db5f2 (4/8) (0 seconds passed, remaining 0 predicted) rm 'config.js' Rewrite 0637c9659623644cfceb35be10f2a1fe5c468e04 (5/8) (0 seconds passed, remaining 0 predicted) rm 'config.js' Rewrite 6c421eb99adc6b987cff7f3cada31e9313638072 (6/8) (0 seconds passed, remaining 0 predicted) rm 'config.js' Rewrite 98001e5b97270efa4a8ab5bd0452be56dd76883d (7/8) (0 seconds passed, remaining 0 predicted) rm 'config.js' Rewrite 2ca4e161a4af2b8f38c46faf848fdbb3e550f23c (8/8) (0 seconds passed, remaining 0 predicted) rm 'config.js' Ref 'refs/heads/secret_keys' was rewritten.

Yup you need https://github.com/newren/git-filter-repo Take a look at https://github.com/newren/git-filter-repo/blob/main/INSTALL.md for instructions

git filter-repo: a third-party command actually, as a replacement to Git's own filter-branch, that allows rewriting the whole history of a repository to remove a mistakenly added file, or help extract part of the repository to another.

I needed to archive some old repositories into a monorepo and of course I gave myself the requirement of maintaining git history, in some way. I tried a couple of solutions but it wasn't until I stumbled upon the git-filter-repo project at https://github.com/newren/git-filter-repo and another article which I've since lost (which was badly documented anyway) that I was able to figure out how to do this.

Git objects are not designed to be changed, they are immutable blobs. This is not a problem if you are making a reader, but is a problem when you want to change things, tools like old git-filter-branch or the newer filter repo abstract all reference updating away for you

Make sure your gitignore is setup right (GitHub has a repo of good defaults). If you messed that up, you could rewrite git history to remove the big stuff. Use git-filter-repo. Not sure how that works for LFS.

git-filter-repo

Check out git filter repo https://github.com/newren/git-filter-repo

I personally prefer git-bfg ( https://rtyley.github.io/bfg-repo-cleaner/ ) ... though git-filter-repo ( https://github.com/newren/git-filter-repo ) is quite popular. The difference for me was that git-bfg is JVM based and my work machine has Java on it while git-filter-repo is python based... and my work machine is without python.