Fix auto head response feature (#1835).

ktor-http/common/src/io/ktor/http/HttpMethod.kt

@@ -4,11 +4,25 @@
 
 package io.ktor.http
 
+import io.ktor.util.*
+
 /**
  * Represents an HTTP method (verb)
  * @property value contains method name
  */
-data class HttpMethod(val value: String) {
+data class HttpMethod(val value: String, @InternalAPI val aggregate: List<HttpMethod> = listOf()) {
+    /**
+     * Checks if the specified HTTP [method] matches this instance of the HTTP method. Specified method matches if it's
+     * equal to this HTTP method or at least one of methods this HTTP method aggregates.
+     */
+    fun match(method: HttpMethod): Boolean {
+        if (this == method) {
+            return true
+        }
+
+        return aggregate.contains(method) || method.aggregate.contains(this)
+    }
+
     @Suppress("KDocMissingDocumentation", "PublicApiImplicitType")
     companion object {
         val Get = HttpMethod("GET")

ktor-server/ktor-server-core/jvm/src/io/ktor/features/AutoHeadResponse.kt

@@ -33,7 +33,10 @@ object AutoHeadResponse : ApplicationFeature<ApplicationCallPipeline, Unit, Unit
 
                 // Pretend the request was with GET method so that all normal routes and interceptors work
                 // but in the end we will drop the content
-                call.mutableOriginConnectionPoint.method = HttpMethod.Get
+                call.mutableOriginConnectionPoint.method = HttpMethod(
+                    "GET_OR_HEAD",
+                    listOf(HttpMethod.Get, HttpMethod.Head)
+                )
             }
         }
     }