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cloning_git_in_go_gophercon_india.pdf
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Aditya Mukerjee
February 25, 2017
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cloning_git_in_go_gophercon_india.pdf
Aditya Mukerjee
February 25, 2017
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Transcript
Cloning Git in Go Aditya Mukerjee Risk & Systems Engineer
at Stripe @chimeracoder
Why write Gitgo? •Git operations from Go applications •Portability •Simplicity
•…why not? @chimeracoder
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
What We’ve Enabled •Backup •Content management •Distributed build systems •Establishing
consensus @chimeracoder
Have you ever seen a “friend’s” computer that looked like
this? @chimeracoder
@chimeracoder 107724969b2af751a1ffd74e3f38d0d76cb8aa55
@chimeracoder commits trees blobs objects
Discovery #1: Layered interfaces are more flexible than union types
@chimeracoder commits trees blobs objects
Bootstrapping Git in Go “We can just use the real
.git directory for our tests, right?” @chimeracoder …nope.
hash(“I love Go”) != hash(“I love Go!”) @chimeracoder Packfiles
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> + “!”
Discovery #2: Pay attention to interface contracts @chimeracoder zlib data
<arbitrary data> zlib data <arbitrary data>
@chimeracoder type Reader interface { Read(p []byte) (n int, err
error) } Object 1 Object 2 Object 3 Object 4 …
• Discovery #3: Use concurrency to define state machines, and
use channels for the input/output @chimeracoder f1 f3 f2 g g1 if f g2
• Discovery #4: Treat errors as values, and ask how
they behave @chimeracoder httpdir.Open() ParsePackfile() GitFetch()
• Discovery #5: Well-architected interfaces perform very well @chimeracoder
#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
Aditya Mukerjee @chimeracoder https://github.com/ChimeraCoder
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