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Comment by mixedmath | Hacker News Reader

This is a really well written partial set of release notes. I was curious and looked at the full release notes [1], and I think these are pretty well written as well. I'm very impressed, especially given that git has such a large set of contributors.

[1]: https://github.com/git/git/blob/v2.11.0/Documentation/RelNot...

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Another nice writeup from Atlassian:

https://news.ycombinator.com/item?id=13066516

I liked this gem in L547:

> The code that we have used for the past 10+ years to cycle 4-element ring buffers turns out to be not quite portable in theoretical world.

That piqued my curiousity, and I had to dig up the relevant commit: https://github.com/git/git/commit/bb84735c80.

It deals with wrapping an integer index around after incrementing it, the old code just used ++index and a bitmask, the new code uses + 1 and modulo.

I have problems understanding this right now, in my world ++index for an int really shouldn't trigger overflow when counting to at most 4, on any (sem-)realistic environment?

Feeling extra dense, must have more coffee.

The counter never resets, it just keeps going up and we only look at the low bits. So eventually it will need to wrap. It's doubtful that ever happened in practice, even on a 32-bit system (you'd need to print 2 billion SHA-1s in a single process, and even the largest repos have on the order of millions).

So the key difference between the old and the new is that the counter resets to zero every fourth call.

Ah, right, that was the thing I failed to see. Obvious now, of course. :) Thanks.

In Git Rev News edition 20 (https://git.github.io/rev_news/2016/10/19/edition-20/) there are also articles about some changes in v2.11:

- Changing the default for “core.abbrev”?

- Prepare the sequencer for the upcoming rebase -i patches

(I am a Git Rev News editor.)

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