Avoid printing "reason unknown" for extract entries

This was happening when the main Gradle User Home entry was not saved due to
having an unchanged cache key.

Fixes #309

src/cache-base.ts

@@ -94,11 +94,18 @@ export class GradleStateCache {
     async save(listener: CacheListener): Promise<void> {
         const cacheKey = generateCacheKey(this.cacheName).key
         const restoredCacheKey = core.getState(RESTORED_CACHE_KEY_KEY)
-        const entryListener = listener.entry(this.cacheDescription)
+        const gradleHomeEntryListener = listener.entry(this.cacheDescription)
 
         if (restoredCacheKey && cacheKey === restoredCacheKey) {
             core.info(`Cache hit occurred on the cache key ${cacheKey}, not saving cache.`)
-            entryListener.markUnchanged('cache key not changed')
+
+            for (const entryListener of listener.cacheEntries) {
+                if (entryListener === gradleHomeEntryListener) {
+                    entryListener.markUnsaved('cache key not changed')
+                } else {
+                    entryListener.markUnsaved(`referencing '${this.cacheDescription}' cache entry not saved`)
+                }
+            }
             return
         }
 
@@ -111,7 +118,7 @@ export class GradleStateCache {
 
         core.info(`Caching ${this.cacheDescription} with cache key: ${cacheKey}`)
         const cachePath = this.getCachePath()
-        await saveCache(cachePath, cacheKey, entryListener)
+        await saveCache(cachePath, cacheKey, gradleHomeEntryListener)
 
         return
     }

src/cache-extract-entries.ts

@@ -213,7 +213,7 @@ abstract class AbstractEntryExtractor {
 
         if (previouslyRestoredKey === cacheKey) {
             cacheDebug(`No change to previously restored ${artifactType}. Not saving.`)
-            entryListener.markUnchanged('contents unchanged')
+            entryListener.markUnsaved('contents unchanged')
         } else {
             core.info(`Caching ${artifactType} with path '${pattern}' and cache key: ${cacheKey}`)
             await saveCache([pattern], cacheKey, entryListener)

src/cache-reporting.ts

@@ -64,7 +64,7 @@ export class CacheEntryListener {
     savedKey: string | undefined
     savedSize: number | undefined
 
-    unchanged: string | undefined
+    unsaved: string | undefined
 
     constructor(entryName: string) {
         this.entryName = entryName
@@ -98,8 +98,8 @@ export class CacheEntryListener {
         return this
     }
 
-    markUnchanged(message: string): CacheEntryListener {
+    markUnsaved(message: string): CacheEntryListener {
-        this.unchanged = message
+        this.unsaved = message
         return this
     }
 }
@@ -159,8 +159,8 @@ function getRestoredMessage(entry: CacheEntryListener, isCacheWriteOnly: boolean
 }
 
 function getSavedMessage(entry: CacheEntryListener, isCacheReadOnly: boolean): string {
-    if (entry.unchanged) {
+    if (entry.unsaved) {
-        return `(Entry not saved: ${entry.unchanged})`
+        return `(Entry not saved: ${entry.unsaved})`
     }
     if (entry.savedKey === undefined) {
         if (isCacheReadOnly) {
@@ -190,11 +190,8 @@ function getSize(
 }
 
 function formatSize(bytes: number | undefined): string {
-    if (bytes === undefined) {
+    if (bytes === undefined || bytes === 0) {
         return ''
     }
-    if (bytes === 0) {
-        return '0 (Entry already exists)'
-    }
     return `${Math.round(bytes / (1024 * 1024))} MB (${bytes} B)`
 }