Add tasks for closing and releasing Sonatype release repository

gradle/publishing.gradle

@@ -1,5 +1,17 @@
+import io.codearte.gradle.nexus.BaseStagingTask
+import io.codearte.gradle.nexus.NexusStagingPlugin
+
 import javax.naming.ConfigurationException
 
+buildscript {
+    repositories {
+        gradlePluginPortal()
+    }
+    dependencies {
+        classpath 'io.codearte.gradle.nexus:gradle-nexus-staging-plugin:0.11.0'
+    }
+}
+
 def releaseVersion = !version.toString().endsWith('-SNAPSHOT')
 
 ext {
@@ -13,6 +25,8 @@ ext {
             project.findProperty('sonatype.username')
     sonatypePassword = project.findProperty('javacord.sonatype.password') ?:
             project.findProperty('sonatype.password')
+    sonatypeStagingProfileId = project.findProperty('javacord.sonatype.stagingProfileId') ?:
+            project.findProperty('sonatype.stagingProfileId')
 }
 
 allprojects {
@@ -88,3 +102,36 @@ allprojects {
         sign publishing.publications
     }
 }
+
+apply plugin: NexusStagingPlugin
+// remove superfluous tasks from NexusStagingPlugin
+tasks.removeAll([promoteRepository, closeAndPromoteRepository, getStagingProfile])
+
+nexusStaging {
+    stagingProfileId sonatypeStagingProfileId
+    username sonatypeUsername
+    password sonatypePassword
+}
+
+// make sure the staging tasks are run after any publishing tasks if both are to be run
+tasks.withType(BaseStagingTask) {
+    mustRunAfter allprojects.tasks*.withType(PublishToMavenRepository)
+
+    doFirst {
+        if (!sonatypeStagingProfileId) {
+            throw new ConfigurationException(
+                    'Please set the Sonatype staging profile id with project property "sonatype.stagingProfileId" ' +
+                            'or "javacord.sonatype.stagingProfileId". If both are set, the latter will be effective.')
+        }
+        if (!sonatypeUsername) {
+            throw new ConfigurationException(
+                    'Please set the Sonatype username with project property "sonatype.username" ' +
+                            'or "javacord.sonatype.username". If both are set, the latter will be effective.')
+        }
+        if (!sonatypePassword) {
+            throw new ConfigurationException(
+                    'Please set the Sonatype password with project property "sonatype.password" ' +
+                            'or "javacord.sonatype.password". If both are set, the latter will be effective.')
+        }
+    }
+}