Upgrade to latest JPI + Gradle versions

Releases were broken with the previous version of the JPI plugin [0],
therefore we needed to try upgrading to the latest version.

As the latest version requires Gradle 6, we have a few changes to make:

- `jenkinsVersion` needs to be referenced through `project.properties`
- the `war` plugin needs to be explicitly added
- the CSS/JS plugins we're using are not yet released[1][2], so we can
  follow the tricks in Spotless[3] to use the version from the (pinned)
  latest commit on GitHub

Next, as we're upgrading the JPI plugin, we need to:

- migrate to using `implementation` / `testImplementation`
- add Feature Variants for each of the `optionalJenkinsPlugins` -
  although I'm not sure if they're needed right now, we'll produce them
  for now and review later

See also https://groups.google.com/g/jenkinsci-dev/c/CDVvgj9dDMs

[0]: jenkinsci/gradle-jpi-plugin#192
[1]: eriwen/gradle-css-plugin#58
[2]: eriwen/gradle-js-plugin#177
[3]: https://github.com/diffplug/spotless/blob/a7f25eb51c6d4006591ea911157e62d0213e320b/CONTRIBUTING.md

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionSha256Sum=abc10bcedb58806e8654210f96031db541bcd2d6fc3161e81cb0572d6a15e821
-distributionUrl=https\://services.gradle.org/distributions/gradle-5.6.4-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.9-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists

job-dsl-api-viewer/build.gradle

@@ -14,8 +14,8 @@ buildscript {
 }
 
 plugins {
-    id 'com.eriwen.gradle.css' version '2.14.0'
-    id 'com.eriwen.gradle.js' version '2.14.1'
+    id 'com.eriwen.gradle.css'
+    id 'com.eriwen.gradle.js'
 }
 
 apply plugin: 'org.ajoberstar.git-publish'

job-dsl-plugin/build.gradle

@@ -11,7 +11,23 @@ buildscript {
 }
 
 plugins {
-    id 'org.jenkins-ci.jpi' version '0.38.0'
+    id 'org.jenkins-ci.jpi' version '0.43.0'
+    id 'war'
+}
+
+java {
+    registerFeature('vsphereCloud') {
+        usingSourceSet(sourceSets.main)
+    }
+    registerFeature('configFileProvider') {
+        usingSourceSet(sourceSets.main)
+    }
+    registerFeature('managedScripts') {
+        usingSourceSet(sourceSets.main)
+    }
+    registerFeature('configurationAsCode') {
+        usingSourceSet(sourceSets.main)
+    }
 }
 
 description = 'Jenkins plugin to leverage job-dsl-core to programmatic create jobs from inside Jenkins.'
@@ -20,7 +36,7 @@ description = 'Jenkins plugin to leverage job-dsl-core to programmatic create jo
 def generatedSourcesDir = 'generated'
 
 jenkinsPlugin {
-    coreVersion = jenkinsVersion
+    coreVersion = project.properties['jenkinsVersion']
     displayName = 'Job DSL'
     url = 'https://github.com/jenkinsci/job-dsl-plugin'
     gitHubUrl = 'https://github.com/jenkinsci/job-dsl-plugin'
@@ -94,18 +110,18 @@ dependencies {
     compile(project(':job-dsl-core'))  {
         exclude group: 'org.jvnet.hudson', module:'xstream'
     }
-    jenkinsPlugins 'org.jenkins-ci.plugins:cloudbees-folder:5.14'
-    jenkinsPlugins 'org.jenkins-ci.plugins:structs:1.19'
-    jenkinsPlugins 'org.jenkins-ci.plugins:script-security:1.54'
-    optionalJenkinsPlugins('org.jenkins-ci.plugins:vsphere-cloud:1.1.11') {
+    implementation 'org.jenkins-ci.plugins:cloudbees-folder:5.14'
+    implementation 'org.jenkins-ci.plugins:structs:1.19'
+    implementation 'org.jenkins-ci.plugins:script-security:1.54'
+    vsphereCloudImplementation('org.jenkins-ci.plugins:vsphere-cloud:1.1.11') {
         exclude group: 'dom4j'
     }
-    optionalJenkinsPlugins 'org.jenkins-ci.plugins:config-file-provider:2.15.4'
-    optionalJenkinsPlugins 'org.jenkinsci.plugins:managed-scripts:1.3'
-    optionalJenkinsPlugins 'io.jenkins:configuration-as-code:1.15'
-    jenkinsTest 'io.jenkins:configuration-as-code:1.15'
-    jenkinsTest 'io.jenkins:configuration-as-code:1.15:tests'
-    jenkinsTest 'org.jenkins-ci.plugins:matrix-auth:1.3'
-    jenkinsTest 'org.jenkins-ci.plugins:nested-view:1.14'
-    jenkinsTest 'org.jenkins-ci.plugins:credentials:2.1.10'
+    configFileProviderImplementation 'org.jenkins-ci.plugins:config-file-provider:2.15.4'
+    managedScriptsImplementation 'org.jenkinsci.plugins:managed-scripts:1.3'
+    configurationAsCodeImplementation 'io.jenkins:configuration-as-code:1.15'
+    testImplementation 'io.jenkins:configuration-as-code:1.15'
+    testImplementation 'io.jenkins:configuration-as-code:1.15:tests'
+    testImplementation 'org.jenkins-ci.plugins:matrix-auth:1.3'
+    testImplementation 'org.jenkins-ci.plugins:nested-view:1.14'
+    testImplementation 'org.jenkins-ci.plugins:credentials:2.1.10'
 }

settings.gradle

@@ -1,2 +1,20 @@
+pluginManagement {
+    repositories {
+        gradlePluginPortal()
+		maven {
+			url 'https://jitpack.io'
+		}
+    }
+    resolutionStrategy {
+        eachPlugin {
+            if (requested.id.id == 'com.eriwen.gradle.css') {
+                useModule('com.github.eriwen:gradle-css-plugin:9fe88d7')
+            } else if (requested.id.id == 'com.eriwen.gradle.js') {
+                useModule('com.github.eriwen:gradle-js-plugin:d15f4ae')
+            }
+        }
+    }
+}
+
 rootProject.name = 'job-dsl-plugin-root'
 include 'job-dsl-core', 'job-dsl-plugin', 'job-dsl-api-viewer'