cloning_git_in_go_gophercon_india.pdf

Transcript

1. Cloning Git in Go Aditya Mukerjee Risk & Systems Engineer

   at Stripe @chimeracoder

2. Why write Gitgo? •Git operations from Go applications •Portability •Simplicity

   •…why not? @chimeracoder

3. The dirty secret about Git •Git wasn’t always meant to

   be a version control system •Git is a decentralized, userland filesystem for preserving historical state and synchronizing data @chimeracoder

4. What We’ve Enabled •Backup •Content management •Distributed build systems •Establishing

   consensus @chimeracoder

5. Have you ever seen a “friend’s” computer that looked like

   this? @chimeracoder

6. @chimeracoder 107724969b2af751a1ffd74e3f38d0d76cb8aa55

7. @chimeracoder commits trees blobs objects

8. Discovery #1: Layered interfaces are more flexible than union types

   @chimeracoder commits trees blobs objects

9. Bootstrapping Git in Go “We can just use the real

   .git directory for our tests, right?” @chimeracoder …nope.

10. hash(“I love Go”) != hash(“I love Go!”) @chimeracoder Packfiles

11. Reference: Unpacking Git Packfiles Reference: Implementing Git’s Compression Algorithm in

    Go binarydiff(1, 2, 3) 1. “I love Go” 2. “I love Go!” 3. “You love Go, and so do I!” “I love Go” <string 1> + “!”

12. Discovery #2: Pay attention to interface contracts @chimeracoder zlib data

    <arbitrary data> zlib data <arbitrary data>

13. @chimeracoder type Reader interface { Read(p []byte) (n int, err

    error) } Object 1 Object 2 Object 3 Object 4 …

14. • Discovery #3: Use concurrency to define state machines, and

    use channels for the input/output @chimeracoder f1 f3 f2 g g1 if f g2

15. • Discovery #4: Treat errors as values, and ask how

    they behave @chimeracoder httpdir.Open() ParsePackfile() GitFetch()

16. • Discovery #5: Well-architected interfaces perform very well @chimeracoder

17. #1: Layered interfaces are more flexible than union types #2:

    Pay attention to interface contracts #3: Use concurrency to define state machines, and use channels for the input/output #4: Treat errors as values, and ask how they behave #5: Well-architected interfaces perform very well @chimeracoder

18. Aditya Mukerjee @chimeracoder https://github.com/ChimeraCoder

19. Further References • “Unpacking Git Packfiles”: https://codewords.recurse.com/issues/three/unpacking-git-packfiles/ • Gitgo: https://github.com/ChimeraCoder/gitgo/

    • “Git from the Inside Out”: https://codewords.recurse.com/issues/two/git-from-the-inside-out @chimeracoder