Add deprecation notice (jorgecarleitao#1429)

README.md

@@ -15,47 +15,68 @@ for a general introduction on how to use this crate, and
 [API docs](https://jorgecarleitao.github.io/arrow2/main/docs/arrow2)
 for a detailed documentation of each of its APIs.
 
+## 2023-04-12: Deprecation Notice
+
+Development has been merged with [Apache Arrow Rust (arrow-rs)], see [#arrow1176] and [#1429].
+
+The arrow2 codebase will continue to be maintained, at least in the short-term, to allow people time to migrate,
+however, codebases are encouraged to migrate to using arrow-rs.
+
+Recent versions of arrow2 provide [interoperability] with arrow-rs to facilitate this. Feel free to raise any issues,
+functionality or otherwise, in the [Apache Arrow Issue Tracker]
+
+[interoperability]: https://github.com/jorgecarleitao/arrow2/pull/1446
+
+[Apache Arrow Rust (arrow-rs)]: https://github.com/apache/arrow-rs
+
+[#arrow1176]: https://github.com/apache/arrow-rs/issues/1176
+
+[Apache Arrow Issue Tracker]: https://github.com/apache/arrow-rs/issues
+
+[#1429]: https://github.com/jorgecarleitao/arrow2/issues/1429
+
 ## Features
 
 * Most feature-complete implementation of Apache Arrow after the reference implementation (C++)
-  * Decimal 256 unsupported (not a Rust native type)
+    * Decimal 256 unsupported (not a Rust native type)
 * C data interface supported for all Arrow types (read and write)
 * C stream interface supported for all Arrow types (read and write)
 * Full interoperability with Rust's `Vec`
 * MutableArray API to work with bitmaps and arrays in-place
 * Full support for timestamps with timezones, including arithmetics that take
   timezones into account
 * Support to read from, and write to:
-  * CSV
-  * Apache Arrow IPC (all types)
-  * Apache Arrow Flight (all types)
-  * Apache Parquet (except deep nested types)
-  * Apache Avro (all types)
-  * NJSON
-  * ODBC (some types)
+    * CSV
+    * Apache Arrow IPC (all types)
+    * Apache Arrow Flight (all types)
+    * Apache Parquet (except deep nested types)
+    * Apache Avro (all types)
+    * NJSON
+    * ODBC (some types)
 * Extensive suite of compute operations
-  * aggregations
-  * arithmetics
-  * cast
-  * comparison
-  * sort and merge-sort
-  * boolean (AND, OR, etc) and boolean kleene
-  * filter, take
-  * hash
-  * if-then-else
-  * nullif
-  * temporal (day, month, week day, hour, etc.)
-  * window
-  * ... and more ...
+    * aggregations
+    * arithmetics
+    * cast
+    * comparison
+    * sort and merge-sort
+    * boolean (AND, OR, etc) and boolean kleene
+    * filter, take
+    * hash
+    * if-then-else
+    * nullif
+    * temporal (day, month, week day, hour, etc.)
+    * window
+    * ... and more ...
 * Extensive set of cargo feature flags to reduce compilation time and binary size
 * Fully-decoupled IO between CPU-bounded and IO-bounded tasks, allowing
   this crate to both be used in `async` contexts without blocking and leverage parallelism
-* Fastest known implementation of Avro and Parquet (e.g. faster than the official 
+* Fastest known implementation of Avro and Parquet (e.g. faster than the official
   C++ implementations)
 
 ## Safety and Security
 
 This crate uses `unsafe` when strictly necessary:
+
 * when the compiler can't prove certain invariants and
 * FFI
 
@@ -79,6 +100,7 @@ We are actively addressing this.
 ## Integration tests
 
 Our tests include roundtrip against:
+
 * Apache Arrow IPC (both little and big endian) generated by C++, Java, Go, C# and JS
   implementations.
 * Apache Parquet format (in its different configurations) generated by Arrow's C++ and
@@ -97,10 +119,13 @@ we also use the `0.x.y` versioning, since we are iterating over the API.
 This repo and crate's primary goal is to offer a safe Rust implementation of the Arrow specification.
 As such, it
 
-* MUST NOT implement any logical type other than the ones defined on the arrow specification, [schema.fbs](https://github.com/apache/arrow/blob/master/format/Schema.fbs).
+* MUST NOT implement any logical type other than the ones defined on the arrow
+  specification, [schema.fbs](https://github.com/apache/arrow/blob/master/format/Schema.fbs).
 * MUST lay out memory according to the [arrow specification](https://arrow.apache.org/docs/format/Columnar.html)
-* MUST support reading from and writing to the [C data interface](https://arrow.apache.org/docs/format/CDataInterface.html) at zero-copy.
-* MUST support reading from, and writing to, the [IPC specification](https://arrow.apache.org/docs/python/ipc.html), which it MUST verify against golden files available [here](https://github.com/apache/arrow-testing).
+* MUST support reading from and writing to
+  the [C data interface](https://arrow.apache.org/docs/format/CDataInterface.html) at zero-copy.
+* MUST support reading from, and writing to, the [IPC specification](https://arrow.apache.org/docs/python/ipc.html),
+  which it MUST verify against golden files available [here](https://github.com/apache/arrow-testing).
 
 Design documents about each of the parts of this repo are available on their respective READMEs.
 
@@ -131,11 +156,12 @@ expectations about API stability that are incompatible with this effort.
 
 Licensed under either of
 
- * Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
- * MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
+* Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
+* MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
 
 at your option.
 
 ### Contribution
 
-Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.
+Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as
+defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.