Validate Gitea runner instance URL

scripts/runner-up.sh

@@ -16,6 +16,21 @@ if grep -q 'replace-with-.*-runner-token' "$ENV_FILE"; then
   exit 1
 fi
 
+INSTANCE_URL="$(sed -n 's/^GITEA_INSTANCE_URL=//p' "$ENV_FILE" | tail -n 1)"
+if [ -z "$INSTANCE_URL" ] || [ "$INSTANCE_URL" = "https://your-gitea.example.com" ]; then
+  echo "missing GITEA_INSTANCE_URL in $ENV_FILE" >&2
+  exit 1
+fi
+
+if command -v curl >/dev/null 2>&1; then
+  version_url="${INSTANCE_URL%/}/api/v1/version"
+  if ! curl -fsS "$version_url" >/dev/null 2>&1; then
+    echo "GITEA_INSTANCE_URL does not look reachable as a Gitea API endpoint: $version_url" >&2
+    echo "Use the exact Gitea web URL, not only the SSH host name." >&2
+    exit 1
+  fi
+fi
+
 cd "$RUNNER_DIR"
 docker compose up -d
 docker compose ps