check_for_new_github_commit.sh

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

# === Configuration ===
GITHUB_USER="USER"
REPO_NAME="REPO"
BRANCH="main"
LAST_COMMIT_FILE=".last_commit"

# GitHub API URL for the branch
GIT_URL="https://github.com/${GITHUB_USER}/${REPO_NAME}.git"

# Fetch the latest remote SHA
LATEST_COMMIT_SHA=$(git ls-remote "$GIT_URL" "$BRANCH" | awk '{print $1}')

if [[ -z "$LATEST_COMMIT_SHA" ]]; then
  echo "Error: couldn't retrieve SHA"
  exit 1
fi

# If no SHA is stored yet, store it and notify
if [[ ! -f "$LAST_COMMIT_FILE" ]]; then
  echo "$LATEST_COMMIT_SHA" > "$LAST_COMMIT_FILE"
  echo "First run – Commit SHA stored: $LATEST_COMMIT_SHA"
  exit 0
fi

# Load previously known SHA
LAST_KNOWN_COMMIT=$(<"$LAST_COMMIT_FILE")

# Compare
if [[ "$LATEST_COMMIT_SHA" != "$LAST_KNOWN_COMMIT" ]]; then
  echo "New commit found: $LATEST_COMMIT_SHA"
  echo "$LATEST_COMMIT_SHA" > "$LAST_COMMIT_FILE"
else
  echo "No new commit – everything is up to date."
fi