chore: add missing trampolinerc (#28)

Author: averikitsch

.trampolinerc

@@ -0,0 +1,61 @@
+# Copyright 2024 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Add required env vars here.
+required_envvars+=(
+)
+
+# Add env vars which are passed down into the container here.
+pass_down_envvars+=(
+    "NOX_SESSION"
+    ###############
+    # Docs builds
+    ###############
+    "STAGING_BUCKET"
+    "V2_STAGING_BUCKET"
+    ##################
+    # Samples builds
+    ##################
+    "INSTALL_LIBRARY_FROM_SOURCE"
+    "RUN_TESTS_SESSION"
+    "BUILD_SPECIFIC_GCLOUD_PROJECT"
+    # Target directories.
+    "RUN_TESTS_DIRS"
+    # The nox session to run.
+    "RUN_TESTS_SESSION"
+)
+
+# Prevent unintentional override on the default image.
+if [[ "${TRAMPOLINE_IMAGE_UPLOAD:-false}" == "true" ]] && \
+   [[ -z "${TRAMPOLINE_IMAGE:-}" ]]; then
+   echo "Please set TRAMPOLINE_IMAGE if you want to upload the Docker image."
+   exit 1
+fi
+
+# Define the default value if it makes sense.
+if [[ -z "${TRAMPOLINE_IMAGE_UPLOAD:-}" ]]; then
+    TRAMPOLINE_IMAGE_UPLOAD=""
+fi
+
+if [[ -z "${TRAMPOLINE_IMAGE:-}" ]]; then
+    TRAMPOLINE_IMAGE=""
+fi
+
+if [[ -z "${TRAMPOLINE_DOCKERFILE:-}" ]]; then
+    TRAMPOLINE_DOCKERFILE=""
+fi
+
+if [[ -z "${TRAMPOLINE_BUILD_FILE:-}" ]]; then
+    TRAMPOLINE_BUILD_FILE=""
+fi