Added the query cache type cases as well, update some documentation

SDWebImage/Core/SDWebImageDefine.h

@@ -260,7 +260,7 @@ FOUNDATION_EXPORT SDWebImageContextOption _Nonnull const SDWebImageContextImageP
 FOUNDATION_EXPORT SDWebImageContextOption _Nonnull const SDWebImageContextImageThumbnailPixelSize;
 
 /**
- A SDImageCacheType raw value which specify the source of cache to query. For example, you can query memory only, query disk only, or query from both memory and disk cache.
+ A SDImageCacheType raw value which specify the source of cache to query. Specify `SDImageCacheTypeDisk` to query from disk cache only; `SDImageCacheTypeMemory` to query from memory only. And `SDImageCacheTypeAll` to query from both memory cache and disk cache. Specify `SDImageCacheTypeNone` is invalid and totally ignore the cache query.
  If not provide or the value is invalid, we will use `SDImageCacheTypeAll`. (NSNumber)
  */
 FOUNDATION_EXPORT SDWebImageContextOption _Nonnull const SDWebImageContextQueryCacheType;

Tests/Tests/SDWebImageManagerTests.m

@@ -294,6 +294,29 @@
     [self waitForExpectationsWithCommonTimeout];
 }
 
+- (void)test15ThatQueryCacheTypeWork {
+    XCTestExpectation *expectation = [self expectationWithDescription:@"Image query cache type works"];
+    NSURL *url = [NSURL URLWithString:@"http://via.placeholder.com/101x101.png"];
+    NSString *key = [SDWebImageManager.sharedManager cacheKeyForURL:url];
+    NSData *testImageData = [NSData dataWithContentsOfFile:[self testJPEGPath]];
+    [SDImageCache.sharedImageCache storeImageDataToDisk:testImageData forKey:key];
+    
+    // Query memory first
+    [SDWebImageManager.sharedManager loadImageWithURL:url options:SDWebImageFromCacheOnly context:@{SDWebImageContextQueryCacheType : @(SDImageCacheTypeMemory)} progress:nil completed:^(UIImage * _Nullable image, NSData * _Nullable data, NSError * _Nullable error, SDImageCacheType cacheType, BOOL finished, NSURL * _Nullable imageURL) {
+        expect(image).beNil();
+        expect(cacheType).equal(SDImageCacheTypeNone);
+        // Query disk secondly
+        [SDWebImageManager.sharedManager loadImageWithURL:url options:SDWebImageFromCacheOnly context:@{SDWebImageContextQueryCacheType : @(SDImageCacheTypeDisk)} progress:nil completed:^(UIImage * _Nullable image2, NSData * _Nullable data2, NSError * _Nullable error2, SDImageCacheType cacheType2, BOOL finished2, NSURL * _Nullable imageURL2) {
+            expect(image2).notTo.beNil();
+            expect(cacheType2).equal(SDImageCacheTypeDisk);
+            [SDImageCache.sharedImageCache removeImageFromDiskForKey:key];
+            [expectation fulfill];
+        }];
+    }];
+    
+    [self waitForExpectationsWithCommonTimeout];
+}
+
 - (NSString *)testJPEGPath {
     NSBundle *testBundle = [NSBundle bundleForClass:[self class]];
     return [testBundle pathForResource:@"TestImage" ofType:@"jpg"];

Tests/Tests/SDWebImageTestCache.m

@@ -188,6 +188,7 @@ static NSString * const SDWebImageTestDiskCacheExtendedAttributeName = @"com.hac
             } else if ([self.diskCache containsDataForKey:key]) {
                 containsCacheType = SDImageCacheTypeDisk;
             }
+            break;
         default:
             break;
     }