feat: adds script for git migration.

scripts/split_repo_migration/git-migrate-history.sh

@@ -0,0 +1,156 @@
+#!/bin/bash
+# Copyright 2023 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
+#
+#     https://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 -ex
+
+[[ "${BASH_SOURCE[0]}" != "${0}" ]] && EXIT=return || EXIT=exit
+
+if [ $# -lt 4 ]
+then
+  echo "Usage: $0 <source-repo> <target-repo> <source-path> <target-path> [folders,to,skip] [files,to,keep] [branch-name]"
+  $EXIT 1
+fi
+
+# source GitHub repository. format: <owner>/<repo>
+SOURCE_REPO=$1
+
+# destination GitHub repository. format: <owner>/<repo>
+TARGET_REPO=$2
+
+# path in the source repo to copy code from. Defaults to the root directory
+SOURCE_PATH=$3
+
+# path in the target repo to put the copied code
+TARGET_PATH=$4
+
+# comma-separated list of files/folders to skip
+IGNORE_FOLDERS=$5
+# keep these specific files that would otherwise be deleted by IGNORE_FOLDERS
+KEEP_FILES=$6
+
+# override the HEAD branch name for the migration PR
+BRANCH=$7
+
+
+if [[ -z "${BRANCH}" ]]
+then
+  # default the branch name to be generated from the source repo name
+  BRANCH=$(basename ${SOURCE_REPO})-migration
+fi
+export FILTER_BRANCH_SQUELCH_WARNING=1
+
+# create a working directory
+WORKDIR="$(mktemp -d -t code-migration-XXXXXXXXXX)"
+echo "Created working directory: ${WORKDIR}"
+
+pushd "${WORKDIR}"  # cd into workdir
+
+echo "Cloning source repository: ${SOURCE_REPO}"
+git clone "git@github.com:${SOURCE_REPO}.git" source-repo
+
+pushd source-repo
+git remote remove origin
+
+# prune only files within the specified directory
+if [[ ! -z "${SOURCE_PATH}" ]]
+then
+  echo "Pruning commits only including path: ${SOURCE_PATH}"
+  git filter-branch \  # rewrites history... unsafe
+    --prune-empty \
+    --subdirectory-filter "${SOURCE_PATH}"
+fi
+
+if [[ ! -z "${IGNORE_FOLDERS}" ]]
+then
+  echo "Ignoring folder: ${IGNORE_FOLDERS}"
+  mkdir -p "${WORKDIR}/filtered-source"
+  FOLDERS=$(echo ${IGNORE_FOLDERS} | tr "," " ")
+  # remove files/folders we don't want
+  FILTER="(rm -rf ${FOLDERS} || true)"
+  if [[ ! -z "${KEEP_FILES}" ]]
+  then
+    KEEP_FILES_SPACES=($(echo ${KEEP_FILES} | tr "," " "))
+    LAST_ELEMENT=$(( ${#KEEP_FILES_SPACES[@]} - 1 ))
+    KEEP_FILE_COMMANDS=""
+    for file in "${KEEP_FILES_SPACES[@]}"
+    do
+      if [[ $file == "${KEEP_FILES_SPACES[$LAST_ELEMENT]}" ]]
+      then
+        KEEP_FILE_COMMANDS+="git checkout -- ${file} 2>/dev/null || true"
+      else 
+        KEEP_FILE_COMMANDS+="git checkout -- ${file} 2>/dev/null || true; "
+      fi   
+    done
+    # restore files to keep, silence errors if the file doesn't exist
+    FILTER="${FILTER}; ${KEEP_FILE_COMMANDS}"
+  fi
+  git filter-branch \
+    --force \
+    --prune-empty \
+    --tree-filter "${FILTER}"
+fi
+
+# reorganize the filtered code into the desired target locations
+if [[ ! -z "${TARGET_PATH}" ]]
+then
+  echo "Moving files to destination path: ${TARGET_PATH}"
+  git filter-branch \
+    --force \
+    --prune-empty \
+    --tree-filter \
+      "shopt -s dotglob; mkdir -p ${WORKDIR}/migrated-source; mv * ${WORKDIR}/migrated-source; mkdir -p ${TARGET_PATH}; mv ${WORKDIR}/migrated-source/* ${TARGET_PATH}"
+fi
+
+# back to workdir
+popd
+
+# merge histories
+echo "Cloning target repository: ${SOURCE_REPO}"
+git clone "git@github.com:${TARGET_REPO}.git" target-repo
+pushd target-repo
+
+git remote add --fetch migration ../source-repo
+git checkout -b "${BRANCH}"
+git merge --allow-unrelated-histories migration/main --no-edit
+
+echo "Success"
+
+popd # back to workdir
+
+# Do a diff between source code split repo and migrated code.
+git clone "git@github.com:${SOURCE_REPO}.git" source-repo-validation  # Not ideal to clone again.
+rm -rf source-repo-validation/.git  # That folder is not needed for validation.
+
+if diff -r target-repo/"${TARGET_PATH}" source-repo-validation; then
+  echo "No diff"
+else
+  diff -r target-repo/"${TARGET_PATH}" source-repo-validation > "diff.txt"
+  echo "Diff non-empty. See ${WORKDIR}/diff.txt"
+  $EXIT 1
+fi
+
+pushd target-repo  # To target repo
+
+git push -u origin "${BRANCH}" --force
+
+# create pull request
+if gh --help > /dev/null
+then
+  gh pr create --title "migrate code from ${SOURCE_REPO}"
+else
+  hub pull-request -m "migrate code from ${SOURCE_REPO}"
+fi
+
+popd

scripts/split_repo_migration/run.sh

@@ -0,0 +1,56 @@
+#!/bin/bash
+# Copyright 2023 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
+#
+#     https://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 -e
+
+[[ "${BASH_SOURCE[0]}" != "${0}" ]] && EXIT=return || EXIT=exit
+
+if [ $# -lt 2 ]
+then
+  echo "Usage: $0 <split-repo-name> <target-path>"
+  $EXIT 1
+fi
+
+# repo name (e.g. nodejs-asset)
+SPLIT_REPO=$1
+# destination directory (e.g. google-cloud-asset)
+ARTIFACT_NAME=$2
+
+## Get the directory of the build script
+SCRIPT_DIR=$(realpath $(dirname "${BASH_SOURCE[0]}"))
+
+export PACKAGE_PATH="packages/${ARTIFACT_NAME}"
+
+# Args to migrate git
+# 1. source GitHub repository. format: <owner>/<repo>
+# 2. destination GitHub repository. format: <owner>/<repo>
+# 3. path in the source repo to copy code from. Defaults to the root directory
+# 4. path in the target repo to put the copied code
+# 5. comma-separated list of files/folders to skip
+# 6. keep these specific files that would otherwise be deleted by IGNORE_FOLDERS
+# 7. override the HEAD branch name for the migration PR
+# 8. path for update script.
+
+echo ${PACKAGE_PATH}
+
+# run the migrate script, remove .kokoro and .github folders
+# keep the .github/.OwlBot.yaml config
+${SCRIPT_DIR}/git-migrate-history.sh \
+  "googleapis/${SPLIT_REPO}" \
+  "googleapis/google-cloud-python" \
+  "" \
+  "${PACKAGE_PATH}" \
+  "" \
+  ".github/.OwlBot.yaml"