Add logging for cache retrieval in GitbookIncrementalCache (#4231)

Author: conico974

packages/gitbook/openNext/incrementalCache/incrementalCache.ts

@@ -29,6 +29,7 @@ export class GitbookIncrementalCache implements IncrementalCache {
         cacheType?: CacheType
     ): Promise<WithLastModified<CacheValue<CacheType>> | null> {
         const cacheKey = this.getR2Key(key, cacheType);
+        console.log(`[GitbookIncrementalCache] Getting cache for key: ${cacheKey}`, key, cacheType);
 
         const r2 = getCloudflareContext().env[BINDING_NAME];
         if (!r2) throw new Error('No R2 bucket');