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0 pointsluckydude5y ago0 comments

I think if you are asking this question either I have completely failed to explain why weaves are cool or you haven't read what I said about why weaves are cool.

Patch based systems are idiotic, that's RCS, that is decades old technology that we know sucks (I've had a cocktail, it's 5pm, so salt away).

Do you understand the difference between pass by reference and pass by value? You must, but in case you don't, you can pass by reference in sizeof(void *), 4-8 bytes. Pass by value and you are copying sizeof(whatever it is you are passing) onto the stack. Obviously, pass by reference is immensely faster.

But in SCM, it isn't just about speed (and space), it's about authorship. In a patch based systems, imagine that there is user A who is doing all the work on the trunk, there is user B who is doing all the work on a branch, and then there is user U who is merging the branch to the trunk. Lets say B added a bunch of work on the branch, it all automerged. U did the merge. In a patch based system, all of the B work is going to be copied (passed by value) to the trunk and the authorship of that work will change from B to U (since U did the merge).

Flip forward to a month from now, the code has paniced or asserted, whatever, B's code on the trunk took a crap. And people are running git blame to see who did that and who did it, U did. But U didn't, B did but U merged it and it was a copy so it looks like U did it.

That's just the SCM being dishonest because it has no choice, it is pass by value.

Weaves are pass by reference. If you merged in BitKeeper and it automerged, you run blame (we call it annotate but I should make blame be an alias if I haven't already, I'm the guy that came up with blame as that verb), you would only see A and B as the authors.

Weaves mean authorship is correct and that whole repack nonsense that Git does? Yeah, that goes away, you are passing every thing by reference so there is only one copy of the code no matter how many branches it has been merged from/to.

Anyone who is pushing a patch based system (and Git is one as well) just doesn't have a clue about how to do source management. Maybe something better than a weave will come along (and if it does, rbsmith will do it, that guy bug fixed my crappy weave implementation) but I think it will just be a better weave with new operators like MOVE (current weaves know INSERT and DELETE, that's it).

Sorry if I'm being a dick, not looking for sympathy but I've got health problems, my feet hurt like crazy and I get kind of terse at the end of the day. If you truly want to understand more, and this goes for all of hacker news, I'm happy to get on a zoom call and talk this stuff through. And it is blindingly obvious I need to write up the SCCS weave and I will do so, you guys have inspired this 58 year old, burned out, can't code to save his life, dude to at least try and pass on some knowledge. I would love to be working with some young person who has some juice and pass on what I know. I don't know everything about SCM but I know a lot. I'm done, it's time for someone else to carry things forward, I'll help if you want. The world deserves a better answer than what we have now.

0 comments

neolog5y ago

I'd be interested to see a conversation between you and the Pijul author. He hangs out in the forum at https://discourse.pijul.org/ and the chat at https://pijul.zulipchat.com/.

pmeunier5y ago

Turns out I also hang out here sometimes ;-)

I was about to reply point by point with arguments, but I changed my mind:

I don't think I'd be interested in that conversation, the comment above is worse than a public display of a very poor understanding of Git and Pijul: it also shows a complete ignorance of other actors in the market. It turns out the market leader for big repositories, Perforce, is itself based on RCS, possibly (but I don't know for sure, since Perforce is proprietary) because RCS scales much better to large binary assets than other solutions (I'd argue Pijul solves that, but that's beside my point).

I am a big fan of Git, Mercurial and Darcs myself, my co-author on Pijul was actually a maintainer of Darcs for many years, and I'm actively collaborating with the maintainers of Mercurial at the moment. And even though Perforce and Plastic are closed-source, they do solve one problem (scalability) which distributed systems are only beginning to understand (if there's one thing I think we've achieved with Pijul, it is about getting beyond the "distributed vs. scalable" trade-off).

Here's my take on the comment above: I don't think you can build good systems without understanding how others are made. There are no free lunches, no silver bullets, no geniuses. Only good ideas, bibliography, and hard work.

luckydudeOP5y ago

I've built two commercially successful systems, NSElite that was used to develop the Solaris kernel and was productized as Avocet/CodeManager/TeamWare (don't blame me, I didn't name it), and BitKeeper which was, at one point, in use on every continent other than the Arctic. If you are running on a 5 year old Intel CPU, that was developed using BitKeeper.

The comment that RCS scales for binaries couldn't be more wrong, RCS hates binaries with a passion.

The fact that you didn't address any of the points I raised says you either don't understand what a weave file format is, or, you do, you recognize it is a much better format but don't want to talk about that.

This part of this thread reminds of something Ron Minnich once said: "Don't worry about people stealing your ideas, you are going to have to cram them down their throats".

I'll drop it, we can revisit when I write up how weaves work. I don't think any objective person would argue that a patch based system is as good, let alone better.

3 more replies

pmeunier5y ago

(Also, our Discourse and Zulip have been pretty civil places until now, I'd like to keep it that way).

j / k navigate · click thread line to collapse

0 comments

neolog5y ago

I'd be interested to see a conversation between you and the Pijul author. He hangs out in the forum at https://discourse.pijul.org/ and the chat at https://pijul.zulipchat.com/.

pmeunier5y ago

Turns out I also hang out here sometimes ;-)

I was about to reply point by point with arguments, but I changed my mind:

luckydudeOP5y ago

The comment that RCS scales for binaries couldn't be more wrong, RCS hates binaries with a passion.

This part of this thread reminds of something Ron Minnich once said: "Don't worry about people stealing your ideas, you are going to have to cram them down their throats".

I'll drop it, we can revisit when I write up how weaves work. I don't think any objective person would argue that a patch based system is as good, let alone better.

3 more replies

pmeunier5y ago

(Also, our Discourse and Zulip have been pretty civil places until now, I'd like to keep it that way).

j / k navigate · click thread line to collapse