Apply plugin repository credentials for dependency graph plugin

sources/src/resources/init-scripts/gradle-actions.github-dependency-graph-gradle-plugin-apply.groovy

@@ -4,13 +4,29 @@ buildscript {
       return System.getProperty(name) ?: System.getenv(envVarName)
   }
   def pluginRepositoryUrl = getInputParam('gradle.plugin-repository.url') ?: 'https://plugins.gradle.org/m2'
+  def pluginRepositoryUsername = getInputParam('gradle.plugin-repository.username')
+  def pluginRepositoryPassword = getInputParam('gradle.plugin-repository.password')
   def dependencyGraphPluginVersion = getInputParam('dependency-graph-plugin.version') ?: '1.2.2'
 
+  logger.lifecycle("Resolving dependency graph plugin ${dependencyGraphPluginVersion} from plugin repository: ${pluginRepositoryUrl}")
   repositories {
-    maven { url pluginRepositoryUrl }
+    maven { 
+      url pluginRepositoryUrl 
+      if (pluginRepositoryUsername && pluginRepositoryPassword) {
+        logger.lifecycle("Applying credentials for plugin repository: ${pluginRepositoryUrl}")
+        credentials {
+          username(pluginRepositoryUsername)
+          password(pluginRepositoryPassword)
+        }
+        authentication {
+          basic(BasicAuthentication)
+        }
+      }
+    }
   }
   dependencies {
     classpath "org.gradle:github-dependency-graph-gradle-plugin:${dependencyGraphPluginVersion}"
   }
 }
+
 apply plugin: org.gradle.github.GitHubDependencyGraphPlugin

sources/test/init-scripts/src/test/groovy/com/gradle/gradlebuildaction/TestDependencyGraph.groovy

@@ -36,7 +36,7 @@ class TestDependencyGraph extends BaseInitScriptTest {
         assert reportFile.exists()
 
         where:
-        testGradleVersion << [GRADLE_8_X]
+        testGradleVersion << DEPENDENCY_GRAPH_VERSIONS
     }
 
     def "produces dependency graph with configuration-cache on latest Gradle"() {
@@ -127,6 +127,41 @@ class TestDependencyGraph extends BaseInitScriptTest {
         testGradleVersion << DEPENDENCY_GRAPH_VERSIONS
     }
 
+    def "can configure alternative repository for plugins"() {
+        assumeTrue testGradleVersion.compatibleWithCurrentJvm
+
+        when:
+        def vars = envVars
+        vars.put('GRADLE_PLUGIN_REPOSITORY_URL', 'https://plugins.grdev.net/m2')
+        def result = run(['help', '--info'], initScript, testGradleVersion.gradleVersion, [], vars)
+
+        then:
+        assert reportFile.exists()
+        assert result.output.contains("Resolving dependency graph plugin 1.2.2 from plugin repository: https://plugins.grdev.net/m2")
+
+        where:
+        testGradleVersion << DEPENDENCY_GRAPH_VERSIONS
+    }
+
+    def "can provide credentials for alternative repository for plugins"() {
+        assumeTrue testGradleVersion.compatibleWithCurrentJvm
+
+        when:
+        def vars = envVars
+        vars.put('GRADLE_PLUGIN_REPOSITORY_URL', 'https://plugins.grdev.net/m2')
+        vars.put('GRADLE_PLUGIN_REPOSITORY_USERNAME', 'REPO_USER')
+        vars.put('GRADLE_PLUGIN_REPOSITORY_PASSWORD', 'REPO_PASSWORD')
+        def result = run(['help', '--info'], initScript, testGradleVersion.gradleVersion, [], vars)
+
+        then:
+        assert reportFile.exists()
+        assert result.output.contains("Resolving dependency graph plugin 1.2.2 from plugin repository: https://plugins.grdev.net/m2")
+        assert result.output.contains("Applying credentials for plugin repository: https://plugins.grdev.net/m2")
+
+        where:
+        testGradleVersion << DEPENDENCY_GRAPH_VERSIONS
+    }
+
     def getEnvVars() {
         return [
             GITHUB_DEPENDENCY_GRAPH_ENABLED: "true",