add mirroring to github using gitlab-ci.yml

Author: Diepenbruck

.gitlab-ci.yml

@@ -1,8 +1,25 @@
-stages:
-  - build
+stages: [mirror]
 
-build-job:
-  stage: build
+mirror_github_mirror_to_github:
+  stage: mirror
+  image: alpine:3.19
+  rules:
+    - if: '$CI_COMMIT_BRANCH == "github_mirror"'
+  before_script:
+    - apk add --no-cache git
+    - git config --global user.email "ci@mirror.local"
+    - git config --global user.name "GitLab CI Mirror"
   script:
-    - echo "Compiling the code..."
-    - echo "Compile complete."
+    # Create a bare clone of the GitLab repo (fast + good for pushing refs)
+    - git clone --bare "$CI_REPOSITORY_URL" repo.git
+    - cd repo.git
+
+    # Add GitHub as a remote (PAT auth via env vars)
+    - git remote add github "https://${GITHUB_USER}:${GITHUB_TOKEN}@github.com/${GITHUB_OWNER}/${GITHUB_REPO}.git"
+
+    # Fetch refs from GitLab origin (to ensure we have the latest)
+    - git fetch origin
+
+    # Push ONLY github_mirror -> rag-sphere
+    # Use --force if you want GitHub to exactly match (history rewrites allowed).
+    - git push --force github "refs/heads/github_mirror:refs/heads/rag-sphere"