Make Slack notification step optional

* Simply some `if:` expressions
* Document how to run release workflow
* Add `on: schedule:` example
* Add warning into docs about nested reusable workflow levels

Author: artembilan

Diff for: .github/workflows/spring-artifactory-release.yml

@@ -20,6 +20,8 @@ on:
         required: false
       GRADLE_ENTERPRISE_SECRET_ACCESS_KEY:
         required: false
+      SPRING_RELEASE_SLACK_WEBHOOK_URL:
+        required: false
       GH_ACTIONS_REPO_TOKEN:
         required: true
       OSSRH_URL:
@@ -36,8 +38,6 @@ on:
         required: true
       JF_ARTIFACTORY_SPRING:
         required: true
-      SPRING_RELEASE_SLACK_WEBHOOK_URL:
-        required: true
 
 env:
   GITHUB_TOKEN: ${{ secrets.GH_ACTIONS_REPO_TOKEN }}

Diff for: .github/workflows/spring-finalize-release.yml

@@ -10,7 +10,7 @@ on:
 
     secrets:
       SPRING_RELEASE_SLACK_WEBHOOK_URL:
-        required: true
+        required: false
       GH_ACTIONS_REPO_TOKEN:
         required: true
 
@@ -52,13 +52,14 @@ jobs:
             gh api -X PATCH repos/$GITHUB_REPOSITORY/milestones/$MILESTONE_ID -f state='closed' --silent
           fi
 
-#      - name: Announce Release on Slack
-#        uses: slackapi/[email protected]
-#        env:
-#          SLACK_WEBHOOK_URL: ${{ secrets.SPRING_RELEASE_SLACK_WEBHOOK_URL }}
-#          SLACK_WEBHOOK_TYPE: INCOMING_WEBHOOK
-#        with:
-#          payload: |
-#            {
-#              "text": "${{ github.event.repository.name }}-announcing `${{ env.MILESTONE }}`"
-#            }
+      - name: Announce Release on Slack
+        uses: slackapi/[email protected]
+        if: env.SLACK_WEBHOOK_URL
+        env:
+          SLACK_WEBHOOK_URL: ${{ secrets.SPRING_RELEASE_SLACK_WEBHOOK_URL }}
+          SLACK_WEBHOOK_TYPE: INCOMING_WEBHOOK
+        with:
+          payload: |
+            {
+              "text": "${{ github.event.repository.name }}-announcing `${{ env.MILESTONE }}`"
+            }

Diff for: .github/workflows/spring-stage-release.yml

@@ -55,7 +55,7 @@ jobs:
 
   staging-with-gradle:
     needs: maven-or-gradle
-    if: ${{ needs.maven-or-gradle.outputs.isMaven == 'false' }}
+    if: needs.maven-or-gradle.outputs.isMaven == 'false'
     uses: ./.github/workflows/spring-artifactory-gradle-release-staging.yml
     with:
       releaseVersion: ${{ inputs.releaseVersion }}
@@ -65,7 +65,7 @@ jobs:
 
   staging-with-maven:
     needs: maven-or-gradle
-    if: ${{ needs.maven-or-gradle.outputs.isMaven == 'true' }}
+    if: needs.maven-or-gradle.outputs.isMaven == 'true'
     uses: ./.github/workflows/spring-artifactory-maven-release-staging.yml
     with:
       releaseVersion: ${{ inputs.releaseVersion }}

Diff for: README.md

@@ -20,6 +20,7 @@ GPG_PRIVATE_KEY
 ```
 
 The Gradle Enterprise secrets are optional: not used by Maven and Gradle project might not be enrolled for the service.  
+The `SPRING_RELEASE_SLACK_WEBHOOK_URL` secret is also optional: probably you don't want to notify Slack about your release.
 
 The mentioned secrets must be passed explicitly since these reusable workflows might be in different GitHub org than target project.
 
@@ -71,7 +72,7 @@ This job stages released artifacts using JFrog CLI into `libs-staging-local` rep
 - When verification is successful, next job promotes release from staging either to `libs-milestone-local` or `libs-release-local`(and Maven Central) according to the releasing version schema
 - Then [spring-finalize-release.yml](.github/workflows/spring-finalize-release.yml) job is executed, which generates release notes using [Spring Changelog Generator](https://github.com/spring-io/github-changelog-generator) excluding repository admins from `Contributors` section.
 The `gh release create` command is performed on a tag for just released version.
-And in the end the milestone is closed and specific Slack channel is notified about release.
+And in the end the milestone is closed and specific Slack channel is notified about release (if `SPRING_RELEASE_SLACK_WEBHOOK_URL` secret is present in the repository).
 
 #### Example of Release caller workflow:
 https://github.com/artembilan/spring-messaging-build-tools/blob/decee2963c926c34f1f52bf373a3bc1dc09f1724/samples/release.yml#L1-L25
@@ -82,6 +83,15 @@ The `buildToolArgs` parameter for this job means extra build tool arguments.
 For example, the mentioned `dist` value is a Gradle task in the project.
 Can be any Maven goal or other command line arguments.
 
+In the end you just need to go to the `Actions` tab on your project, press `Run workflow` on your release workflow and choose a branch from drop-down list to release currently scheduled Milestone against. 
+Such a release workflow can also be scheduled (`cron`, fo example) against branches matrix:
+
+
+> **Warning**
+> The [spring-artifactory-release.yml](.github/workflows/spring-artifactory-release.yml) already uses 3 of 4 levels of nested reusable workflows.
+> Where the caller workflow is the last one.
+> Therefore don't try to reuse your caller workflow. 
+
 ## Verify Staged Artifacts
 
 The `verify-staged` job expects an optional `verifyStagedWorkflow` input (the `verify-staged-artifacts.yml`, by default) workflow supplied from the target project.
@@ -96,3 +106,5 @@ https://github.com/artembilan/spring-messaging-build-tools/blob/dbd138bf504abec5
 Gradle projects must not manage `com.jfrog.artifactory` plugin anymore: the `jf gradlec` command sets up this plugin and respective tasks into a project using JFrog specific Gradle init script.
 In addition, the [spring-artifactory-gradle-snapshot.yml](.github/workflows/spring-artifactory-gradle-snapshot.yml) and [spring-artifactory-gradle-release-staging.yml](.github/workflows/spring-artifactory-gradle-release-staging.yml) add `spring-project-init.gradle` script to provide an `artifactory` plugin settings for artifacts publications.
 This script also adds a `nextDevelopmentVersion` task which is used when release has been staged and job is ready to push `Next development version` commit.
+
+See more information in the [Reusing Workflows](https://docs.github.com/en/actions/using-workflows/reusing-workflows). 

Diff for: samples/schedule-releases.yml

@@ -0,0 +1,19 @@
+name: Release Scheduler
+on:
+  schedule:
+    - cron: '15 15 * * MON' # Every Monday at 3:15pm UTC
+
+jobs:
+  dispatch_scheduled_releases:
+    strategy:
+      matrix:
+        # List of active maintenance branches.
+        branch: [ main, 6.1.x, 6.0.x, 5.8.x ]
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Dispatch
+        env:
+          GITHUB_TOKEN: ${{ secrets.GH_ACTIONS_REPO_TOKEN }}
+        run: gh workflow run release.yml -r ${{ matrix.branch }}