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Pijul is based on a different (and much more advanced) algorithm than Git. That doesn't mean it's the perfect tool - just as Git is better than SVN (even though

by tomp 8y ago

Pijul is based on a different (and much more advanced) algorithm than Git. That doesn't mean it's the perfect tool - just as Git is better than SVN (even though they're based on the same underlying algorithms), Pijul might be the "SVN-like" tool waiting for its own Git... Edit: having said that, Git isn't perfect either, I'm keeping my fingers crossed for an even better tool!

DaiPlusPlus 8y ago
> just as Git is better than SVN (even though they're based on the same underlying algorithms) Please explain this. Git is a content-addressable object-store. SVN is not. SVN’s architecture uses a diff as the basis for versioning which ties you to a particular diffing system, git uses snapshots and diffs can be generated using any algorithm because they aren’t part of the object-store; so what common “underlying algorithms” are you referring to?
- tomp 8y ago
  AFAIK the basic merge algorithm for both Git and SVN is 3-way diff. Pijul instead uses commutative patches and a more complex merge algorithm.
  - arghwhat 8y ago
    Is it a better merge algorithm? Complexity on its own is not a selling point. And if it is better, then I believe that it should also be possible to implement for Git, as the patch properties of Pijul and Darcs can easily be emulated.
    - tomp 8y ago
      Well if it's better at preventing bad merges, it's better, yes. Pijul might not be the best/optimal implementation of this algorithm, but it's still a step in the right direction (mainly because they optimized the algorithm significantly, reducing its complexity). Like, not all benefits of number theory (e.g. encryption) were discovered on the first day either.
    - pmeunier 8y ago
      1. It is associative, which make it predictable, and yes, better. 2. It is commutative, which makes it non-trivial to emulate with Git, a system where nothing commutes (on purpose). Of course, you can obviously do your merges manually, rebase the world at each new commit, cherry-pick and rerere to emulate what Pijul gives you for free. But then is your job writing code or showing your proficiency at Git?
- geezerjay 8y ago
  > Please explain this. Git is a content-addressable object-store. SVN is not. They are both version control systems. People use them to track versions, as well as merging changes and diverging development branches. How data s stored is an implementation delail that doesn't reflect on the mental model.
arghwhat 8y ago
Git is extremely different from SVN at all levels. Pijul does not appear particularly different from Git from a high-level perspective, however. Internal implementation details are very different, but they are largely invisible to the user. It appears that Pijul is meant as an enhancement to Darcs (At least, the FAQ makes that out to be the case). Darcs which has its list of key features here: http://darcs.net/Features http://darcs.net/Features, all of which overlap entirely with Git.
- tomp 8y ago
  Indeed, and it differs from Git in the same way as Darcs differs from Git: the basic block of history/code is not a commit, but a (commutative) patch.
  - arghwhat 8y ago
    Yes, which misses the point: Darcs does not mention any features that Git lacks, and lets its differences remain as largely invisible and irrelevant from the perspective of the user.
johnisgood 8y ago
> Pijul might be the "SVN-like" tool waiting for its own Git... Or Pijul is git, and Darcs is SVN in this case.

by tomp 8y ago

DaiPlusPlus 8y ago

> just as Git is better than SVN (even though they're based on the same underlying algorithms) Please explain this. Git is a content-addressable object-store. SVN is not. SVN’s architecture uses a diff as the basis for versioning which ties you to a particular diffing system, git uses snapshots and diffs can be generated using any algorithm because they aren’t part of the object-store; so what common “underlying algorithms” are you referring to?

tomp 8y ago
AFAIK the basic merge algorithm for both Git and SVN is 3-way diff. Pijul instead uses commutative patches and a more complex merge algorithm.
- arghwhat 8y ago
  Is it a better merge algorithm? Complexity on its own is not a selling point. And if it is better, then I believe that it should also be possible to implement for Git, as the patch properties of Pijul and Darcs can easily be emulated.
  - tomp 8y ago
    Well if it's better at preventing bad merges, it's better, yes. Pijul might not be the best/optimal implementation of this algorithm, but it's still a step in the right direction (mainly because they optimized the algorithm significantly, reducing its complexity). Like, not all benefits of number theory (e.g. encryption) were discovered on the first day either.
  - pmeunier 8y ago
    1. It is associative, which make it predictable, and yes, better. 2. It is commutative, which makes it non-trivial to emulate with Git, a system where nothing commutes (on purpose). Of course, you can obviously do your merges manually, rebase the world at each new commit, cherry-pick and rerere to emulate what Pijul gives you for free. But then is your job writing code or showing your proficiency at Git?
geezerjay 8y ago
> Please explain this. Git is a content-addressable object-store. SVN is not. They are both version control systems. People use them to track versions, as well as merging changes and diverging development branches. How data s stored is an implementation delail that doesn't reflect on the mental model.

arghwhat 8y ago

Git is extremely different from SVN at all levels. Pijul does not appear particularly different from Git from a high-level perspective, however. Internal implementation details are very different, but they are largely invisible to the user. It appears that Pijul is meant as an enhancement to Darcs (At least, the FAQ makes that out to be the case). Darcs which has its list of key features here: http://darcs.net/Features http://darcs.net/Features, all of which overlap entirely with Git.

tomp 8y ago
Indeed, and it differs from Git in the same way as Darcs differs from Git: the basic block of history/code is not a commit, but a (commutative) patch.
- arghwhat 8y ago
  Yes, which misses the point: Darcs does not mention any features that Git lacks, and lets its differences remain as largely invisible and irrelevant from the perspective of the user.

johnisgood 8y ago

> Pijul might be the "SVN-like" tool waiting for its own Git... Or Pijul is git, and Darcs is SVN in this case.