git-protocol: git protocol notes, for developers

In pkgdepends: Package Dependency Resolution and Downloads

git protocol notes, for developers

Description

Assumptions, they might be relaxed or checked for later:

• The server must speak the smart protocol, version 1 or 2. (Although I added some functions specifically for the dumb protocol, but they are pretty limited.)

• We use HTTP transport, not SSH.

• The server should have the shallow capability.

• The server should have the filter capability if protocol version 2.

• Only SHA-1 hashing is supported.

Details

Improvements needed:

• DONE Tests. (Can always have more.)

• DONE Use async HTTP.

• DONE Support packfiles with deltas. (ofs-delta objects are still not supported.)

• DONE Optionally send authorization. Already possibly in the URL.

• DONE Better error messages.

• Better errors for non-existing user, repository, ref, PR, etc.

Optional improvements:

• Support ofs-delta objects in packfiles. Not necessarily, unless we send this capability, the server is not sending ofs-delta objects.

• Make unpacking faster. It is not fast currently, with all the bit arithmetic in R. But it is already faster than a tar.gz + uncompress download from GitHub, so not really needed.

Docs and other helpful links:

• https://github.com/git/git/blob/master/Documentation/gitprotocol-common.txt

• https://github.com/git/git/blob/master/Documentation/gitprotocol-pack.txt

• https://github.com/git/git/blob/master/Documentation/gitprotocol-v2.txt

• https://github.com/calebsander/git-internals/blob/part2/src/main.rs

• https://dev.to/calebsander/git-internals-part-1-the-git-object-model-474m

pkgdepends documentation built on Nov. 10, 2023, 5:06 p.m.