How update a git submodule using octokit.js

[zegof]

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I already tried to adopt this one: octokit/octokit.rb#936 / file at this time in octokit.js, but that doesn't worked.

Is there a way to update a git submodule / submodule sha using octokit.js ?

[emmagracebravo-lgtm]

Short answer: there is no single “update submodule” API in Octokit.js. A submodule update is just a commit that changes the submodule gitlink SHA, and you have to do that manually via the Git data APIs.

How it works conceptually

A submodule is stored in the parent repo as a special tree entry that points to a commit SHA in another repo. Updating it means creating a new commit in the parent repo with a new gitlink SHA.

The correct way using Octokit.js

You must:

Get the latest commit SHA of the submodule repo

Create a new tree in the parent repo that updates the submodule entry

Create a commit with that tree

Update the branch reference

Minimal example (Octokit.js)
import { Octokit } from "@octokit/rest";
const octokit = new Octokit({ auth: process.env.GITHUB_TOKEN });

const owner = "OWNER";
const repo = "PARENT_REPO";
const branch = "main";
const submodulePath = "path/to/submodule";

// 1. Get current commit
const { data: ref } = await octokit.git.getRef({
owner,
repo,
ref: heads/${branch},
});

const baseCommitSha = ref.object.sha;

// 2. Get base tree
const { data: baseCommit } = await octokit.git.getCommit({
owner,
repo,
commit_sha: baseCommitSha,
});

// 3. Create new tree with updated submodule SHA
const newSubmoduleSha = "NEW_SUBMODULE_COMMIT_SHA";

const { data: newTree } = await octokit.git.createTree({
owner,
repo,
base_tree: baseCommit.tree.sha,
tree: [
{
path: submodulePath,
mode: "160000", // REQUIRED for submodules
type: "commit",
sha: newSubmoduleSha,
},
],
});

// 4. Create commit
const { data: newCommit } = await octokit.git.createCommit({
owner,
repo,
message: "Update submodule",
tree: newTree.sha,
parents: [baseCommitSha],
});

// 5. Update branch ref
await octokit.git.updateRef({
owner,
repo,
ref: heads/${branch},
sha: newCommit.sha,
});

Important notes

mode: "160000" is mandatory for submodules

You cannot use the Contents API for submodules

This mirrors exactly what git submodule update does locally

TL;DR

Yes, you can update a submodule with Octokit.js, but only by manually creating a commit that updates the gitlink SHA using the Git Data API. There is no shortcut method.

[markjkaem]

Question

Body

I already tried to adopt this one: octokit/octokit.rb#936 / file at this time in octokit.js, but that doesn't worked.

Is there a way to update a git submodule / submodule sha using octokit.js ?

Yeah updating submodules via the API is tricky. You can't directly update the submodule, but you can update the tree entry that points to the submodule commit.
Basically get your current commit with getRef, then create a new tree with createTree where you include an entry with your submodule path, mode "160000" (thats the submodule mode), type "commit", and the new sha you want to point to. Then create a commit with that tree and update the ref.
The key is mode "160000" which tells git its a submodule reference not a regular file.