Wire new init-script into action

- Copy init-script to Gradle User Home
- Rename init-scripts for consistency and clarity

src/resources/init-scripts/gradle-build-action.github-dependency-graph.init.gradle

@@ -0,0 +1,59 @@
+import org.gradle.util.GradleVersion
+
+// Only run when dependency graph is explicitly enabled
+if (System.env.GITHUB_DEPENDENCY_GRAPH_ENABLED != "true") {
+  return
+}
+
+// Do not run for unsupported versions of Gradle
+if (GradleVersion.current().baseVersion < GradleVersion.version("5.0")) {
+  println "::warning::Dependency Graph is not supported for Gradle versions < 5.0. No dependency snapshot will be generated."
+  return
+}
+
+// Attempt to find a unique job correlator to use based on the environment variable
+// This is only required for top-level builds
+def isTopLevelBuild = gradle.getParent() == null
+if (isTopLevelBuild) {
+  def reportFile = getUniqueReportFile(System.env.GITHUB_JOB_CORRELATOR)
+
+  if (reportFile == null) {
+    println "::warning::No dependency snapshot generated for step. Could not determine unique job correlator - specify GITHUB_JOB_CORRELATOR var for this step."
+    return
+  }
+
+  def githubOutput = System.getenv("GITHUB_OUTPUT")
+  if (githubOutput) {
+      new File(githubOutput) << "dependency-graph-file=${reportFile.absolutePath}\n"
+  }
+
+
+  println "Generating dependency graph into '${reportFile}'"
+}
+
+apply from: 'gradle-build-action.github-dependency-graph-gradle-plugin-apply.groovy'
+
+/**
+ * Using the supplied jobCorrelator value:
+ * - Checks if report file already exists
+ * - If so, tries to find a unique value that does not yet have a corresponding report file.
+ * - When found, this value is set as a System property override.
+ */
+File getUniqueReportFile(String jobCorrelator) {
+    def reportDir = System.env.DEPENDENCY_GRAPH_REPORT_DIR
+    def reportFile = new File(reportDir, jobCorrelator + ".json")
+    if (!reportFile.exists()) return reportFile
+
+    // Try at most 100 suffixes
+    for (int i = 1; i < 100; i++) {
+        def candidateCorrelator = jobCorrelator + "-" + i
+        def candidateFile = new File(reportDir, candidateCorrelator + ".json")
+        if (!candidateFile.exists()) {
+           System.properties['GITHUB_JOB_CORRELATOR'] = candidateCorrelator
+           return candidateFile
+        }
+    }
+
+    // Could not determine unique job correlator
+    return null
+}