TUN-9800: Add pipeline to sync between gitlab and github repos

.ci/scripts/github-push.sh

@@ -0,0 +1,31 @@
+#!/bin/bash
+set -e -o pipefail
+
+BRANCH="master"
+TMP_PATH="$PWD/tmp"
+PRIVATE_KEY_PATH="$TMP_PATH/github-deploy-key"
+PUBLIC_KEY_GITHUB_PATH="$TMP_PATH/github.pub"
+
+mkdir -p $TMP_PATH
+
+# Setup Private Key
+echo "$CLOUDFLARED_DEPLOY_SSH_KEY" > $PRIVATE_KEY_PATH
+chmod 400 $PRIVATE_KEY_PATH
+
+# Download GitHub Public Key for KnownHostsFile
+ssh-keyscan -t ed25519 github.com > $PUBLIC_KEY_GITHUB_PATH
+
+# Setup git ssh command with the right configurations
+export GIT_SSH_COMMAND="ssh -o UserKnownHostsFile=$PUBLIC_KEY_GITHUB_PATH -o IdentitiesOnly=yes -i $PRIVATE_KEY_PATH"
+
+# Add GitHub as a new remote
+git remote add github git@github.com:cloudflare/cloudflared.git || true
+
+# GitLab doesn't pull branch references, instead it creates a new one on each pipeline.
+# Therefore, we need to manually fetch the reference to then push it to GitHub.
+git fetch origin $BRANCH:$BRANCH
+git push -u github $BRANCH
+
+if TAG="$(git describe --tags --exact-match 2>/dev/null)"; then
+  git push -u github "$TAG"
+fi