Categorical Theory of Patches

Transcript

1. A Categorical Theory of Patches Hunter Madison hmadison@customink.com @355E3B lobste.rs/3553eb
2. Version Control
3. Time • One direction (forward) • Events (commits) have a distinct order
4. Files • Things on disk • Contain stuff we want to version
5. Patches • Instructions that let us transform one file into a second one
6. Groups and Categories
7. Group • Set of elements, with an operation which combines any two elements to form a third element • The operation satisfies the group axioms (Closure, Associativity, Identity and Invertibility)
8. Category • Objects linked by morphisms (functions) • We only care about Associativity, Identity • Mesh Like
9. Category By IkamusumeFan - Own work, CC BY-SA 4.0, https:// commons.wikimedia.org/w/index.php?curid=36599484
10. Pushout • Two new morphisms which go to some new object
11. Pushout (Yes, this came from the Wikipieda page)
12. Categorical Theory of Patches
13. Linking this up • Files -> Objects • Morphisms -> Patches
14. L • Is the set of all files and patches • Is partially ordered (vs linearly ordered) • We can use a pushout to resolve our merges
15. Merging
16. Merging • I’m skipping this • Myers or Patience diff handles this.
17. Implementation
18. Implementation • Darcs* - http://darcs.net/ • Camp - http://projects.haskell.org/camp/ • Pijul - http://pijul.org/
19. Demo Time
21. This paper, I love • Its not going to replace the one true VCS • But, we can use it to recast to a different model
22. Recasting • Instead of focusing on how to solve corner cases, we can instead find a general solution and build a concrete description • In general, we can do this for any problem
23. Reading List • “A FORMALIZATION OF DARCS PATCH THEORY USING INVERSE SEMIGROUPS” - ftp:// ftp.math.ucla.edu/pub/camreport/cam09-83.pdf • “Camp Path Theory” - http://projects.haskell.org/ camp/files/theory.pdf • “The Theory of patches-vector” - http:// liamoc.net/posts/2015-11-10-patch-theory.html