GH-3175: Add .scanner() to inbound file sync spec

Resolves #3175

* Fix `@since` for backport

**Cherry-pick to `5.2.x`**

(cherry picked from commit 1ff69d4)

Author: garyrussell

spring-integration-file/src/main/java/org/springframework/integration/file/dsl/RemoteFileInboundChannelAdapterSpec.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2016-2019 the original author or authors.
+ * Copyright 2016-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,6 +25,7 @@
 import org.springframework.integration.dsl.ComponentsRegistration;
 import org.springframework.integration.dsl.MessageSourceSpec;
 import org.springframework.integration.expression.FunctionExpression;
+import org.springframework.integration.file.DirectoryScanner;
 import org.springframework.integration.file.filters.ExpressionFileListFilter;
 import org.springframework.integration.file.filters.FileListFilter;
 import org.springframework.integration.file.remote.synchronizer.AbstractInboundFileSynchronizer;
@@ -270,6 +271,17 @@ public S metadataStorePrefix(String metadataStorePrefix) {
 		return _this();
 	}
 
+	/**
+	 * Configure a scanner to use for the file system scan after transfer.
+	 * @param scanner the scanner.
+	 * @return the spec.
+	 * @since 5.2.4
+	 */
+	public S scanner(DirectoryScanner scanner) {
+		this.target.setScanner(scanner);
+		return _this();
+	}
+
 	@Override
 	public Map<Object, String> getComponentsToRegister() {
 		Map<Object, String> componentsToRegister = new LinkedHashMap<>();

spring-integration-ftp/src/test/java/org/springframework/integration/ftp/dsl/FtpTests.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2019 the original author or authors.
+ * Copyright 2014-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,7 +25,9 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.nio.charset.StandardCharsets;
+import java.util.Iterator;
 import java.util.List;
+import java.util.Map;
 import java.util.regex.Matcher;
 
 import org.apache.commons.net.ftp.FTPFile;
@@ -47,6 +49,8 @@
 import org.springframework.integration.dsl.StandardIntegrationFlow;
 import org.springframework.integration.dsl.context.IntegrationFlowContext;
 import org.springframework.integration.dsl.context.IntegrationFlowContext.IntegrationFlowRegistration;
+import org.springframework.integration.file.DefaultDirectoryScanner;
+import org.springframework.integration.file.DirectoryScanner;
 import org.springframework.integration.file.FileHeaders;
 import org.springframework.integration.file.remote.RemoteFileTemplate;
 import org.springframework.integration.file.remote.gateway.AbstractRemoteFileOutboundGateway;
@@ -86,17 +90,24 @@ public class FtpTests extends FtpTestSupport {
 	@Test
 	public void testFtpInboundFlow() throws IOException {
 		QueueChannel out = new QueueChannel();
+		DirectoryScanner scanner = new DefaultDirectoryScanner();
 		IntegrationFlow flow = IntegrationFlows.from(Ftp.inboundAdapter(sessionFactory())
 						.preserveTimestamp(true)
 						.remoteDirectory("ftpSource")
 						.maxFetchSize(10)
+						.scanner(scanner)
 						.regexFilter(".*\\.txt$")
 						.localFilename(f -> f.toUpperCase() + ".a")
 						.localDirectory(getTargetLocalDirectory()),
 				e -> e.id("ftpInboundAdapter").poller(Pollers.fixedDelay(100)))
 				.channel(out)
 				.get();
 		IntegrationFlowRegistration registration = this.flowContext.registration(flow).register();
+		Map<?, ?> components = TestUtils.getPropertyValue(registration, "integrationFlow.integrationComponents", Map.class);
+		Iterator<?> iterator = components.keySet().iterator();
+		iterator.next();
+		Object spcafb = iterator.next();
+		assertThat(TestUtils.getPropertyValue(spcafb, "source.fileSource.scanner")).isSameAs(scanner);
 		Message<?> message = out.receive(10_000);
 		assertThat(message).isNotNull();
 		assertThat(message.getHeaders())