Git Download Manager
Challanges and Opportunities
{
"Speaker": "Gaetano Checinski",
"Company": "LoopPerfect"
"Role": "Founder & Software Architect"
}
Buckaroo - Decentralized Package Manager
How to Downlaod Commit #deadbeef
from git@github.com:loopperfect/RxTerm.git?
Why not ... ?
git clone $URL && git checkout #deadbeef
Does ... work ?
git clone --depth=1 -n $URL && git fetch #deadbeef
Why doesn't it work?
error: Server does not allow request for unadvertised object #deadbeef
What is an Advertised Object?
How to discover all Advertised Objects?
git ls-remote --all
Why doesn't it work? - Part II
- Git needs to compute a diff between the your local commits
and the requested commit, but...
- Git's commits are a singly linked list
- Every commit only knows it's parent
- Heads, Tags are references to a commit
- Which Tag or Head should Git walk to find #deadbeef?
Why doesn't it work? - Part III
Git! Just make it work!
[uploadpack]
allowTipSha1InWant = true
allowReachableSHA1InWant = true
allowAnySHA1InWant = true
Most Git Hosts disable this features
Git Shallow + Fetch + Heuristics
- Use Hints in Manifests and Lockfiles about branches
Git clone --depth=1 -n $URL#branchThatLikelyHasDeadBeefgit fetch --deepen=$N to get N commits- repeat
fetch if commit not found. exponentially increase N - Inspect Datetime and fetched (SemVer-) Tags to determine if you should give up
- Repeat process for alternative branches
- Give up and unshallow Repository by fetching the remaining diffs
How to Copy Commit from (Bare) Repo Cache?
git clone --shared -n path/to/cache.git && git checkout #deadbeef
- All commits in cache.git available in cloned repos
How to Copy Commit from (Bare) Repo Cache II?
git clone --reference path/to/cache.git git@github.com/owner/repo.git
- creates a real clone but speeds up download by using the cache.git