build: add monorepo migration script (#11880)

Usage:

```
MIGRATION_HEAD_BRANCH=main \
  SOURCE_REPO_URL=https://github.com/googleapis/java-datastore \
  SQUASH_COMMITS=true \
  ./monorepo-migration/migrate.sh
```

options:
* `MIGRATION_HEAD_BRANCH` - the code to branch from (e.g. if you need
additional commits before the migration - defaults to `main`
* `SOURCE_REPO_URL` - the split repository to migration - defaults to
`https://github.com/googleapis/java-logging`
* `SQUASH_COMMITS` - if set to `true`, then squash all migration fixes
applied into a single commit

---------

Co-authored-by: Mike Eltsufin <meltsufin@google.com>

Author: chingor13

.kokoro/build.sh

@@ -33,10 +33,27 @@ if [ -f "${KOKORO_GFILE_DIR}/secret_manager/java-bigqueryconnection-samples-secr
   source "${KOKORO_GFILE_DIR}/secret_manager/java-bigqueryconnection-samples-secrets"
 fi
 
+if [[ -n "${BUILD_SUBDIR}" ]]
+then
+  echo "Compiling and building all modules for ${BUILD_SUBDIR}"
+  mvn clean install \
+    -DskipTests \
+    -Dclirr.skip \
+    -Dflatten.skip \
+    -Dcheckstyle.skip \
+    -Djacoco.skip \
+    -Denforcer.skip \
+    --also-make \
+    --projects "${BUILD_SUBDIR}"
+  echo "Running in subdir: ${BUILD_SUBDIR}"
+  pushd "${BUILD_SUBDIR}"
+fi
+
 RETURN_CODE=0
 
 case ${JOB_TYPE} in
   test)
+    echo "SUREFIRE_JVM_OPT: ${SUREFIRE_JVM_OPT}"
     retry_with_backoff 3 10 \
       mvn test \
         -B -ntp \
@@ -48,7 +65,7 @@ case ${JOB_TYPE} in
         -Dflatten.skip=true \
         -Danimal.sniffer.skip=true \
         -Dmaven.wagon.http.retryHandler.count=5 \
-        -T 1C
+        -T 1C ${SUREFIRE_JVM_OPT}
     RETURN_CODE=$?
     echo "Finished running unit tests"
     ;;
@@ -125,6 +142,12 @@ case ${JOB_TYPE} in
 
 esac
 
+if [[ -n "${BUILD_SUBDIR}" ]]
+then
+  echo "restoring directory"
+  popd
+fi
+
 if [ "${REPORT_COVERAGE}" == "true" ]; then
   bash ${KOKORO_GFILE_DIR}/codecov.sh
 fi

.kokoro/dependencies.sh

@@ -49,6 +49,12 @@ function determineMavenOpts() {
 
 export MAVEN_OPTS=$(determineMavenOpts)
 
+if [[ -n "${BUILD_SUBDIR}" ]]
+then
+  echo "Running in subdir: ${BUILD_SUBDIR}"
+  pushd "${BUILD_SUBDIR}"
+fi
+
 # this should run maven enforcer
 retry_with_backoff 3 10 \
   mvn install -B -V -ntp \
@@ -57,3 +63,9 @@ retry_with_backoff 3 10 \
     -Dclirr.skip=true
 
 mvn -B dependency:analyze -DfailOnWarning=true
+
+if [[ -n "${BUILD_SUBDIR}" ]]
+then
+  echo "Leaving subdir: ${BUILD_SUBDIR}"
+  popd
+fi

.kokoro/presubmit/common.cfg

@@ -24,6 +24,12 @@ env_vars: {
   value: "test"
 }
 
+# Well known environment variable to datastore tests
+env_vars: {
+  key: "DATASTORE_PROJECT_ID"
+  value: "cloud-java-ci-test"
+}
+
 before_action {
   fetch_keystore {
     keystore_resource {

generation/check_non_release_please_versions.sh

@@ -19,6 +19,10 @@ for pomFile in $(find . -mindepth 2 -name pom.xml | sort ); do
     echo "Skipping version check for java-samples directory"
     continue
   fi
+  if [[ "${pomFile}" =~ .*/samples/.* ]]; then
+    echo "Skipping version check for samples directory"
+    continue
+  fi
 
   if grep -n '<version>.*</version>' "$pomFile" | grep -v 'x-version-update'; then
     echo "Found version declaration(s) without x-version-update in: $pomFile"

monorepo-migration/fix_copyright_headers.py

@@ -0,0 +1,53 @@
+#!/usr/bin/env python3
+# Copyright 2026 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.
+
+import os
+import re
+import sys
+
+def fix_copyright(path):
+    if os.path.isfile(path):
+        if path.endswith(".java"):
+            _fix_file(path)
+    elif os.path.isdir(path):
+        for root, _, files in os.walk(path):
+            for file in files:
+                if file.endswith(".java"):
+                    _fix_file(os.path.join(root, file))
+
+def _fix_file(file_path):
+    with open(file_path, 'r') as f:
+        content = f.read()
+    
+    # Replace "Copyright [Year] Google LLC" or "Copyright [Year] Google Inc."
+    # with "Copyright 2026 Google LLC"
+    new_content = re.sub(
+        r'Copyright \d{4} Google (Inc\.|LLC)',
+        'Copyright 2026 Google LLC',
+        content
+    )
+    
+    if new_content != content:
+        with open(file_path, 'w') as f:
+            f.write(new_content)
+        print(f"Updated copyright in {file_path}")
+
+if __name__ == "__main__":
+    if len(sys.argv) < 2:
+        print("Usage: fix_copyright_headers.py <file_or_directory_path> ...")
+        sys.exit(1)
+    
+    for arg in sys.argv[1:]:
+        fix_copyright(arg)