Comment by pmeunier | Hacker News Reader

Comment by pmeunier | Hacker News Reader

Parent Full thread

It is not at all about not being Git. The absolute best reason is that Pijul actually has the properties that people think Git has:

- in Pijul, patches are associative: pulling B and C together after A does the same as pulling just C after pulling A and B. Git doesn't have that property: sometimes diff3 randomly (and silently) decides to shuffle lines around.

- in Pijul, patches commute. Most Git users try to simulate that by rebasing branches, but (1) that can mean a lot of extra work for no fundamental reason and (2) Git runs the same clunky merge algorithms to decide how to do it.

- Pijul knows what a conflict is, whereas Git pretends to know, but then there's "git rerere".

- in Pijul, you can clone one subdirectory of a monorepo by just pulling the patches related to that directory. Git can do partial clones as well, but only with LFS and/or submodules, which are incredibly clunky and unnatural.

> patches are associative: pulling B and C together after A does the same as pulling just C after pulling A and B

that makes no sense to me. DARCS also claim this, but if you have the patches all changing the first line to a different value, obviously the last one will dictate the final value of the first line. Which is the same as git. in what world do you want to change orders of patches and not have the final state change?

Associativity is not about changing the order but about a different grouping:

    ( A B ) C = A ( B C )

If A, B and C are patches, you are applying C last on the left side and A last on the right.

You are wrong. Yes, on the left side B is applied to A, then C is applied to the result (AB). However, on the right side, C is applied to B, then the result (BC) is applied to A. A is still the left most patch in both cases. BC could depend on (the output context of) A so it wouldn't make sense to apply A to BC! BC is applied to A. A(BC)

So you are saying that applying patches is not commutative? I was assuming A(BC) == (BC)A. What makes you think that the result should be different depending on the order?

Reply on news.ycombinator.com