release: prepare for initial release 0.2.0

There are plenty of unreleased variants of libsecp256k1 version 0.1.0
(libsecp256k1.so.0.0.0) in the wild. We choose a new version number to allow a
clear distinction.

There are variants of 0.1.0 that are incompatible with the initial release,
hence we increase the minor version to arrive at version number 0.2.0. For the
same reason, we increase the LIB_VERSION_CURRENT and keep AGE at 0.

The changelog for 0.2.0 consists of the relevant changes since 2021-12-25, which
is the date when the initial release process PR was merged (and the library
version was set to a pre-release, see 423b6d1).
This is somewhat arbitrary but at least points readers to relevant changes.

CHANGELOG.md

@@ -1,22 +1,28 @@
 # Changelog
 
-This file is currently only a template for future use.
-
-Each change falls into one of the following categories: Added, Changed, Deprecated, Removed, Fixed or Security.
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## [Unreleased]
 
+## [0.2.0] - 2022-12-12
+
 ### Added
  - Added `secp256k1_selftest`, to be used in conjunction with `secp256k1_context_static`.
 
 ### Changed
- - Enable modules schnorrsig, extrakeys and ECDH by default in ./configure
+ - Enabled modules schnorrsig, extrakeys and ECDH by default in `./configure`.
 
 ### Deprecated
  - Deprecated context flags `SECP256K1_CONTEXT_VERIFY` and `SECP256K1_CONTEXT_SIGN`. Use `SECP256K1_CONTEXT_NONE` instead.
  - Renamed `secp256k1_context_no_precomp` to `secp256k1_context_static`.
 
-## [MAJOR.MINOR.PATCH] - YYYY-MM-DD
+### ABI Compatibility
+
+Since this is the first release, we do not compare application binary interfaces.
+However, there are unreleased versions of libsecp256k1 that are *not* ABI compatible with this version.
+
+## [0.1.0] - 2013-03-05 to 2021-12-25
 
-### Added/Changed/Deprecated/Removed/Fixed/Security
-- [Title with link to Pull Request](https://link-to-pr)
+This version was in fact never released.
+The number was given by the build system since the introduction of autotools in Jan 2014 (ea0fe5a5bf0c04f9cc955b2966b614f5f378c6f6).
+Therefore, this version number does not uniquely identify a set of source files.

configure.ac

@@ -4,16 +4,16 @@ AC_PREREQ([2.60])
 # the API. All changes in experimental modules are treated as
 # backwards-compatible and therefore at most increase the minor version.
 define(_PKG_VERSION_MAJOR, 0)
-define(_PKG_VERSION_MINOR, 1)
+define(_PKG_VERSION_MINOR, 2)
 define(_PKG_VERSION_PATCH, 0)
-define(_PKG_VERSION_IS_RELEASE, false)
+define(_PKG_VERSION_IS_RELEASE, true)
 
 # The library version is based on libtool versioning of the ABI. The set of
 # rules for updating the version can be found here:
 # https://www.gnu.org/software/libtool/manual/html_node/Updating-version-info.html
 # All changes in experimental modules are treated as if they don't affect the
 # interface and therefore only increase the revision.
-define(_LIB_VERSION_CURRENT, 0)
+define(_LIB_VERSION_CURRENT, 1)
 define(_LIB_VERSION_REVISION, 0)
 define(_LIB_VERSION_AGE, 0)