Add tooling for Go-compatible branch.

The WORKSPACE go_repositories can be generated from a standard go.mod file. Add
the necessary gazelle hooks to do so, and include a test that sanity checks
there are no changes. This go.mod file will be used in a subsequent commit to
generate a go gettable branch of the repository.

This commit also adds a tools/go_branch.sh script, which given an existing go
branch in the repository, will add an additional synthetic change to the branch
bringing it up-to-date with HEAD.

As a final step, a cloudbuild script is included, which can be used to automate
the process for every change pushed to the repository. This may be used after
an initial go branch is pushed, but this is manual process.

PiperOrigin-RevId: 251095016

1 files changed, 76 insertions, 0 deletions

diff --git a/tools/go_branch.sh b/tools/go_branch.sh
new file mode 100755
index 000000000..8ea6a6d8d
--- /dev/null
+++ b/tools/go_branch.sh
@@ -0,0 +1,76 @@
+#!/bin/bash
+
+# Copyright 2019 The gVisor Authors.
+#
+# 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.
+
+set -eo pipefail
+
+# Discovery the package name from the go.mod file.
+declare -r gomod="$(pwd)/go.mod"
+declare -r module=$(cat "${gomod}" | grep -E "^module" | cut -d' ' -f2)
+
+# Check that gopath has been built.
+declare -r gopath_dir="$(pwd)/bazel-bin/gopath/src/${module}"
+if ! [ -d "${gopath_dir}" ]; then
+  echo "No gopath directory found; build the :gopath target." >&2
+  exit 1
+fi
+
+# Create a temporary working directory, and ensure that this directory and all
+# subdirectories are cleaned up upon exit.
+declare -r tmp_dir=$(mktemp -d)
+finish() {
+  cd # Leave tmp_dir.
+  rm -rf "${tmp_dir}"
+}
+trap finish EXIT
+
+# Record the current working commit.
+declare -r head=$(git describe --always)
+
+# We expect to have an existing go branch that we will use as the basis for
+# this commit. That branch may be empty, but it must exist.
+declare -r go_branch=$(git show-ref --hash origin/go)
+
+# Clone the current repository to the temporary directory, and check out the
+# current go_branch directory. We move to the new repository for convenience.
+declare -r repo_orig="$(pwd)"
+declare -r repo_new="${tmp_dir}/repository"
+git clone . "${repo_new}"
+cd "${repo_new}"
+
+# Setup the repository and checkout the branch.
+git config user.email "gvisor-bot@google.com"
+git config user.name "gVisor bot"
+git fetch origin "${go_branch}"
+git checkout -b go "${go_branch}"
+
+# Start working on a merge commit that combines the previous history with the
+# current history. Note that we don't actually want any changes yet.
+git merge --allow-unrelated-histories --no-commit --strategy ours ${head}
+
+# Sync the entire gopath_dir and go.mod.
+rsync --recursive --verbose --delete --exclude .git --exclude README.md -L "${gopath_dir}/" .
+cp "${gomod}" .
+
+# There are a few solitary files that can get left behind due to the way bazel
+# constructs the gopath target. Note that we don't find all Go files here
+# because they may correspond to unused templates, etc.
+cp "${repo_orig}"/runsc/*.go runsc/
+
+# Update the current working set and commit.
+git add . && git commit -m "Merge ${head} (automated)"
+
+# Push the branch back to the original repository.
+git remote add orig "${repo_orig}" && git push -f orig go:go