Generate release notes in release pipeline

This commit adds new tasks to the release pipeline, generating release
notes automatically using the issues in the current milestone and
pushing that as the content of the GitHub release.

Closes gh-25922

ci/config/changelog-generator.yml

+changelog:
+  repository: spring-projects/spring-framework
+  sections:
+    - title: ":star: New Features"
+      labels:
+        - "type: enhancement"
+    - title: ":beetle: Bug Fixes"
+      labels:
+        - "type: bug"
+        - "type: regression"
+    - title: ":notebook_with_decorative_cover: Documentation"
+      labels:
+        - "type: documentation"
+    - title: ":hammer: Dependency Upgrades"
+      sort: "title"
+      labels:
+        - "type: dependency-upgrade"

ci/pipeline.yml

@@ -24,9 +24,16 @@ anchors:
     silent: true
     icon_emoji: ":concourse:"
     username: concourse-ci
-  sontatype-task-params: &sonatype-task-params
+  sonatype-task-params: &sonatype-task-params
     SONATYPE_USER_TOKEN: ((sonatype-user-token))
     SONATYPE_PASSWORD_TOKEN: ((sonatype-user-token-password))
+  changelog-task-params: &changelog-task-params
+    name: generated-changelog/tag
+    tag: generated-changelog/tag
+    body: generated-changelog/changelog.md
+  github-task-params: &github-task-params
+    GITHUB_USERNAME: ((github-username))
+    GITHUB_TOKEN: ((github-ci-release-token))
 
 resource_types:
 - name: artifactory-resource
@@ -44,6 +51,7 @@ resource_types:
   source:
     repository: cfcommunity/slack-notification-resource
     tag: latest
+
 resources:
 - name: git-repo
   type: git
@@ -136,6 +144,24 @@ resources:
   icon: slack
   source:
     url: ((slack-webhook-url))
+- name: github-pre-release
+  type: github-release
+  icon: briefcase-download-outline
+  source:
+    owner: spring-projects
+    repository: spring-framework
+    access_token: ((github-ci-release-token))
+    pre_release: true
+    release: false
+- name: github-release
+  type: github-release
+  icon: briefcase-download
+  source:
+    owner: spring-projects
+    repository: spring-framework
+    access_token: ((github-ci-release-token))
+    pre_release: false
+
 jobs:
 - name: build-spring-framework-ci-images
   plan:
@@ -335,6 +361,14 @@ jobs:
       params:
         RELEASE_TYPE: M
         <<: *artifactory-task-params
+    - task: generate-changelog
+      file: git-repo/ci/tasks/generate-changelog.yml
+      params:
+        RELEASE_TYPE: M
+        <<: *github-task-params
+    - put: github-pre-release
+      params:
+        <<: *changelog-task-params
 - name: stage-rc
   serial: true
   plan:
@@ -372,6 +406,14 @@ jobs:
       params:
         RELEASE_TYPE: RC
         <<: *artifactory-task-params
+    - task: generate-changelog
+      file: git-repo/ci/tasks/generate-changelog.yml
+      params:
+        RELEASE_TYPE: RC
+        <<: *github-task-params
+    - put: github-pre-release
+      params:
+        <<: *changelog-task-params
 - name: stage-release
   serial: true
   plan:
@@ -427,6 +469,15 @@ jobs:
       params:
         <<: *bintray-task-params
         <<: *sonatype-task-params
+    - task: generate-changelog
+      file: git-repo/ci/tasks/generate-changelog.yml
+      params:
+        RELEASE_TYPE: RELEASE
+        <<: *github-task-params
+    - put: github-release
+      params:
+        <<: *changelog-task-params
+
 groups:
 - name: "builds"
   jobs: ["build", "jdk11-build", "jdk14-build", "jdk15-build"]

ci/scripts/generate-changelog.sh

+#!/bin/bash
+set -e
+
+CONFIG_DIR=git-repo/ci/config
+version=$( cat version/version )
+
+java -jar /github-changelog-generator.jar \
+  --spring.config.location=${CONFIG_DIR}/changelog-generator.yml \
+  ${version} generated-changelog/changelog.md
+
+echo ${version} > generated-changelog/version
+echo v${version} > generated-changelog/tag

ci/tasks/generate-changelog.yml

+---
+platform: linux
+image_resource:
+  type: docker-image
+  source:
+    repository: springio/github-changelog-generator
+    tag: '0.0.4'
+inputs:
+- name: git-repo
+- name: version
+outputs:
+- name: generated-changelog
+params:
+  GITHUB_ORGANIZATION:
+  GITHUB_REPO:
+  GITHUB_USERNAME:
+  GITHUB_TOKEN:
+  RELEASE_TYPE:
+run:
+  path: git-repo/ci/scripts/generate-changelog.sh