Report the cache as disabled when Gradle User Home exists

Fixes #434

src/cache-reporting.ts

@@ -10,6 +10,7 @@ export class CacheListener {
     cacheReadOnly = false
     cacheWriteOnly = false
     cacheDisabled = false
+    cacheDisabledReason = 'disabled'
 
     get fullyRestored(): boolean {
         return this.cacheEntries.every(x => !x.wasRequestedButNotRestored())
@@ -17,7 +18,7 @@ export class CacheListener {
 
     get cacheStatus(): string {
         if (!cache.isFeatureAvailable()) return 'not available'
-        if (this.cacheDisabled) return 'disabled'
+        if (this.cacheDisabled) return this.cacheDisabledReason
         if (this.cacheWriteOnly) return 'write-only'
         if (this.cacheReadOnly) return 'read-only'
         return 'enabled'

src/caches.ts

@@ -29,6 +29,8 @@ export async function restore(gradleUserHome: string, cacheListener: CacheListen
         core.info('Gradle User Home already exists: will not restore from cache.')
         // Initialize pre-existing Gradle User Home.
         gradleStateCache.init()
+        cacheListener.cacheDisabled = true
+        cacheListener.cacheDisabledReason = 'disabled due to pre-existing Gradle User Home'
         return
     }