add post-checkout to run git prune

fix #321

containers/buildkite-premerge-debian/Dockerfile

@@ -10,6 +10,7 @@ RUN echo 'install buildkite' ;\
 COPY *.sh /usr/local/bin/
 RUN chmod og+rx /usr/local/bin/*.sh
 COPY --chown=buildkite-agent:buildkite-agent pre-checkout /etc/buildkite-agent/hooks
+COPY --chown=buildkite-agent:buildkite-agent post-checkout /etc/buildkite-agent/hooks
 
 ENTRYPOINT ["entrypoint.sh"]
 CMD ["gosu", "buildkite-agent", "buildkite-agent", "start", "--no-color"]

containers/buildkite-premerge-debian/post-checkout

@@ -0,0 +1,25 @@
+# Copyright 2021 Google LLC
+#
+# Licensed under the the Apache License v2.0 with LLVM Exceptions (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://llvm.org/LICENSE.txt
+#
+# 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.
+
+# The `post-checkout` hook runs after checkout.
+
+set -eu
+
+# Run prune as git will start to complain about
+git prune
+if [ -f ".git/gc.log" ]; then
+  echo ".git/gc.log exist"
+  cat ./.git/gc.log
+  rm -f ./.git/gc.log
+fi

containers/buildkite-premerge-debian/pre-checkout

@@ -17,6 +17,7 @@
 # checked out from your SCM provider
 
 set -e
+
 # Convert https://github.com/llvm-premerge-tests/llvm-project.git -> llvm-project
 # to use the same directory for fork and origin.
 BUILDKITE_BUILD_CHECKOUT_PATH="${BUILDKITE_BUILD_PATH}/$(echo $BUILDKITE_REPO | sed -E "s#.*/([^/]*)#\1#" | sed "s/.git$//")"