How to fix fatal: Submodule update failed in CI - shallow clone doesn't support submodules in Git

- uses: actions/checkout@v4
  with:
    fetch-depth: 0  # Fetch all history for all branches and tags
    submodules: recursive  # Checkout submodules

- uses: actions/checkout@v4
  with:
    fetch-depth: 2  # Minimal history, may work for some submodule setups
    submodules: recursive

variables:
  GIT_SUBMODULE_STRATEGY: recursive
  GIT_DEPTH: 0  # Disable shallow clone (0 = full clone)

# Or use GIT_SUBMODULE_DEPTH for submodule-specific depth
variables:
  GIT_SUBMODULE_STRATEGY: recursive
  GIT_SUBMODULE_DEPTH: 0

variables:
  GIT_SUBMODULE_FORCE_HTTPS: "true"  # If using SSH URLs in .gitmodules

pipeline {
    agent any
    stages {
        stage('Checkout') {
            steps {
                checkout([
                    $class: 'GitSCM',
                    branches: [[name: '*/main']],
                    extensions: [
                        [$class: 'SubmoduleOption',
                         disableSubmodules: false,
                         recursiveSubmodules: true,
                         trackingSubmodules: false],
                        [$class: 'CloneOption',
                         depth: 0,  // Full clone
                         noTags: false,
                         shallow: false]
                    ],
                    userRemoteConfigs: [[url: 'https://github.com/your/repo.git']]
                ])
            }
        }
    }
}

version: 2.1

jobs:
  build:
    docker:
      - image: cimg/base:stable
    steps:
      - checkout
      - run:
          name: Initialize submodules with full history
          command: |
            git fetch --unshallow || true
            git submodule sync --recursive
            git submodule update --init --recursive

#!/bin/bash
set -e

# Check if we're in a shallow clone
if [ -f "$(git rev-parse --git-dir)/shallow" ]; then
    echo "Unshallowing repository..."
    git fetch --unshallow
fi

# Sync submodule URLs in case they changed
git submodule sync --recursive

# Initialize and update all submodules
git submodule update --init --recursive

echo "Submodules updated successfully"

- uses: actions/checkout@v4
  with:
    fetch-depth: 0
    submodules: recursive
    ssh-key: ${{ secrets.SUBMODULE_DEPLOY_KEY }}

before_script:
  - eval $(ssh-agent -s)
  - echo "$SSH_PRIVATE_KEY" | tr -d '\r' | ssh-add -
  - mkdir -p ~/.ssh
  - chmod 700 ~/.ssh
  - ssh-keyscan github.com >> ~/.ssh/known_hosts

# In your CI before_script or setup step
git config --global url."https://github.com/".insteadOf "[email protected]:"
git config --global url."https://gitlab.com/".insteadOf "[email protected]:"

# Then update submodules
git submodule sync --recursive
git submodule update --init --recursive

variables:
  GIT_SUBMODULE_FORCE_HTTPS: "true"