git-commit-updated-submodules

#!/usr/bin/env bash
set -euo pipefail

# Run from the superproject root.
cd "$(git rev-parse --show-toplevel)"

# Collect submodule paths from .gitmodules
mapfile -t submodules < <(git config --file .gitmodules --get-regexp path | awk '{print $2}')

if [ "${#submodules[@]}" -eq 0 ]; then
  echo "No submodules found."
  exit 0
fi

updated_any=false

for sub in "${submodules[@]}"; do
  # Skip if submodule is not initialized
  if [ ! -d "$sub" ]; then
    echo "Skipping uninitialized submodule: $sub"
    continue
  fi

  # Commit recorded in superproject HEAD (gitlink)
  recorded_hash="$(git rev-parse "HEAD:$sub" 2>/dev/null || true)"
  # Current commit checked out in submodule
  current_hash="$(git -C "$sub" rev-parse HEAD 2>/dev/null || true)"

  # If current hash differs, submodule pointer needs update in superproject
  if [ -n "$current_hash" ] && [ "$recorded_hash" != "$current_hash" ]; then
    short_hash="$(git -C "$sub" rev-parse --short HEAD)"
    submodule_name="$(basename "$sub")"

    git add "$sub"
    git commit -m "Updated ${submodule_name} to ${short_hash}."

    echo "Committed submodule update: ${submodule_name} -> ${short_hash}"
    updated_any=true
  fi
done

if [ "$updated_any" = false ]; then
  echo "No updated submodules detected."
fi