create CHANGELOG, add #339

closes #167

CHANGELOG.md

@@ -0,0 +1,36 @@
+# Changelog
+
+## 1.0.0
+
+### Revamped authentication support
+
+Integrates [revamped support for authentication from
+docker-client][RegistryAuthSupplier] into the plugin, making it possible for
+the plugin to be more flexible in regards to authentication credentials used
+when pushing/pulling/building images.
+
+Previous versions of the plugin had the limitation of using the same
+RegistryAuth header for all images, regardless of what registries they came
+from.
+
+In this version, the docker-maven-plugin will automatically use any
+authentication present in the docker-cli configuration file at `~/.dockercfg`
+or `~/.docker/config.json`.
+
+Additionally the plugin will enable support for Google Container Registry if it
+is able to successfully load [Google's "Application Default Credentials"][ADC].
+The plugin will also load Google credentials from the file pointed to by the
+environment variable `DOCKER_GOOGLE_CREDENTIALS` if it is defined. Since GCR
+authentication requires retrieving short-lived access codes for the given
+credentials, support for this registry is baked into the underlying
+docker-client rather than having to first populate the docker config file
+before running the plugin.
+
+Lastly, authentication credentials can be explicitly configured in your pom.xml
+and in your Maven installation's `settings.xml` file as part of the
+`<servers></servers>` block.
+
+[339](https://github.com/spotify/docker-maven-plugin/pull/339)
+
+[RegistryAuthSupplier]: https://github.com/spotify/docker-client/blob/dba55b17d09d4a15aa9d26884b22b230d49fce64/docs/user_manual.md#authentication-to-private-registries
+[ADC]: https://developers.google.com/identity/protocols/application-default-credentials