Add README

Author: lhotari

.asf.yaml

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+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you 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.
+#
+
+github:
+  description: "Pulsar SQL extracted from apache/pulsar"
+  homepage: https://pulsar.apache.org/
+  labels:
+    - pulsar
+    - apache-pulsar
+    - trino
+    - pulsar-sql
+    - sql
+  features:
+    # Enable wiki for documentation
+    wiki: true
+    # Enable issues management
+    issues: true
+    # Enable projects for project management boards
+    projects: true
+  enabled_merge_buttons:
+    # enable squash button:
+    squash:  true
+    # disable merge button:
+    merge:   false
+    # disable rebase button:
+    rebase:  false
+notifications:
+  commits:      commits@pulsar.apache.org
+  issues:       commits@pulsar.apache.org
+  pullrequests: commits@pulsar.apache.org
+  discussions:  dev@pulsar.apache.org

README.md

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+# pulsar-sql module extracted from apache/pulsar
+
+### History
+
+Pulsar SQL has been removed from the apache/pulsar repository. Some history:
+
+* In April 2020, it was decided to remove Pulsar SQL from apache/pulsar repository:
+  * https://lists.apache.org/thread/qr49rp91w8pp8ljz1jtxn92ktnznh9tb
+  * https://github.com/apache/pulsar/wiki/PIP-62%3A-Move-connectors%2C-adapters-and-Pulsar-Presto-to-separate-repositories
+* In April 2021, there was a decision to contribute Pulsar SQL as a Trino plugin:
+  * https://lists.apache.org/thread/f9n6sc2mrboq5sxhjbr7gvdl8vqp9fpk
+* This was the status in December 2021:
+  * https://lists.apache.org/thread/gqs9tq3p6tr38b7j6gjbfzfg7z1vkvsd
+  * The Trino PR was https://github.com/trinodb/trino/pull/8020
+  * The work on the plugin stalled and it was never taken to completion.
+* In December 2023, Pulsar SQL was finally removed from the apache/pulsar repository:
+  * https://lists.apache.org/thread/4f1cco12cycq36m7vtyjs2j5q5975666
+* In October 2024, the Pulsar SQL modules were extracted from apache/pulsar to this repository, apache/pulsar-sql.
+
+### Extracting the Pulsar SQL modules with preserved commit history
+
+This repository is a fork of the Pulsar SQL module files that were present in apache/pulsar until [the removal commit](https://github.com/apache/pulsar/commit/c157f0d9). This commit is used to find out the list of removed files. Since the Pulsar SQL modules have been maintained in branch-3.0, the files have been extracted from branch-3.0 on 2024-10-18 to this repository.
+
+It has been extracted from apache/pulsar with the following commands so that the commit history is preserved:
+
+```shell
+git clone https://github.com/apache/pulsar pulsar-sql
+cd pulsar-sql
+# https://github.com/apache/pulsar/commit/c157f0d9 is the commit hash of Pulsar SQL modules removal
+git diff-tree --no-commit-id --name-only --diff-filter=D -r c157f0d > /tmp/keep_files.txt
+# branch-3.0 contains the maintained Pulsar SQL modules
+git checkout branch-3.0
+# also keep all files in the pulsar-sql directory in branch-3.0
+find pulsar-sql >> /tmp/keep_files.txt
+# install git-filter-repo for filtering out the removed Pulsar SQL modules
+brew install git-filter-repo
+# filter out the removed Pulsar SQL modules
+git filter-repo --paths-from-file /tmp/keep_files.txt --force
+# delete the old master branch
+git branch -D master
+# create a new master branch
+git checkout -b master
+```
+
+### Todo
+
+- [ ] Setup a maven build for the separate repository
+  - Reuse apache/pulsar and outdated [apache/pulsar-presto](https://github.com/apache/pulsar-presto) pom.xml and setup parent pom.xml for the separate repository
+- [ ] Setup a GitHub Actions CI pipeline to test the separate repository