Restore/save configuration-cache data in first action

Previously, the action was restoring/saving the configuration-cache data for each
step that applied the action. In order to support Gradle invocations that are _not_
managed by the action, the configuration-cache restore is now performed in the initial
action step, and save is performed in the final post-action step.

The build root directories are recorded for each invocation via an init script.

src/cache-project-dot-gradle.ts

@@ -1,27 +1,52 @@
+import * as core from '@actions/core'
 import path from 'path'
-import {AbstractCache} from './cache-base'
-
-// TODO: Maybe allow the user to override / tweak this set
-const PATHS_TO_CACHE = [
-    'configuration-cache' // Only configuration-cache is stored at present
-]
+import fs from 'fs'
+import {AbstractCache, META_FILE_DIR, PROJECT_ROOTS_FILE} from './cache-base'
 
 /**
  * A simple cache that saves and restores the '.gradle/configuration-cache' directory in the project root.
  */
 export class ProjectDotGradleCache extends AbstractCache {
-    private rootDir: string
-    constructor(rootDir: string) {
-        super('project', 'Project configuration cache')
-        this.rootDir = rootDir
+    constructor(gradleUserHome: string) {
+        super(gradleUserHome, 'project', 'Project configuration cache')
     }
 
     protected getCachePath(): string[] {
-        const dir = this.getProjectDotGradleDir()
-        return PATHS_TO_CACHE.map(x => path.resolve(dir, x))
+        return this.getProjectRoots().map(x => path.resolve(x, '.gradle/configuration-cache'))
     }
 
-    private getProjectDotGradleDir(): string {
-        return path.resolve(this.rootDir, '.gradle')
+    protected initializeGradleUserHome(gradleUserHome: string, initScriptsDir: string): void {
+        const projectRootCapture = path.resolve(initScriptsDir, 'project-root-capture.init.gradle')
+        fs.writeFileSync(
+            projectRootCapture,
+            `
+    // Only run again root build. Do not run against included builds.
+    def isTopLevelBuild = gradle.getParent() == null
+    if (isTopLevelBuild) {
+        settingsEvaluated { settings ->
+            def projectRootEntry = settings.rootDir.absolutePath + "\\n"
+            def projectRootList = new File(settings.gradle.gradleUserHomeDir, "${META_FILE_DIR}/${PROJECT_ROOTS_FILE}")
+            println "Adding " + projectRootEntry + " to " + projectRootList
+            if (!projectRootList.exists() || !projectRootList.text.contains(projectRootEntry)) {
+                projectRootList << projectRootEntry
+            }
+        }
+    }`
+        )
+    }
+
+    /**
+     * For every Gradle invocation, we record the project root directory. This method returns the entire
+     * set of project roots, to allow saving of configuration-cache entries for each.
+     */
+    private getProjectRoots(): string[] {
+        const projectList = path.resolve(this.gradleUserHome, META_FILE_DIR, PROJECT_ROOTS_FILE)
+        if (!fs.existsSync(projectList)) {
+            core.info(`Missing project list file ${projectList}`)
+            return []
+        }
+        const projectRoots = fs.readFileSync(projectList, 'utf-8')
+        core.info(`Found project roots '${projectRoots}' in ${projectList}`)
+        return projectRoots.trim().split('\n')
     }
 }