GH-8659: Fix WatchService to react for renames

Fixes #8659

* GH-8659: Updating the documentation as requested

* GH-8659: Fixes requested after coder review

**Cherry-pick to `6.1.x`, `6.0.x` & `5.5.x`**

Author: pziobron

spring-integration-file/src/main/java/org/springframework/integration/file/FileReadingMessageSource.java

@@ -93,6 +93,7 @@
  * @author Gary Russell
  * @author Artem Bilan
  * @author Steven Pearce
+ * @author Patryk Ziobron
  */
 public class FileReadingMessageSource extends AbstractMessageSource<File> implements ManageableLifecycle {
 
@@ -533,6 +534,11 @@ private void processFilesFromNormalEvent(Set<File> files, File parentDir, WatchE
 			logger.debug(() -> "Watch event [" + event.kind() + "] for file [" + file + "]");
 
 			if (StandardWatchEventKinds.ENTRY_DELETE.equals(event.kind())) {
+				Path filePath = file.toPath();
+				if (this.pathKeys.containsKey(filePath)) {
+					WatchKey watchKey = this.pathKeys.remove(filePath);
+					watchKey.cancel();
+				}
 				if (getFilter() instanceof ResettableFileListFilter<File> resettableFileListFilter) {
 					resettableFileListFilter.remove(file);
 				}
@@ -554,7 +560,7 @@ private void processFilesFromNormalEvent(Set<File> files, File parentDir, WatchE
 				}
 				else {
 					logger.debug(() -> "A file [" + file + "] for the event [" + event.kind() +
-							"] doesn't exist. Ignored.");
+							"] doesn't exist. Ignored. Maybe DELETE event is not watched ?");
 				}
 			}
 		}

src/reference/asciidoc/file.adoc

@@ -371,6 +371,11 @@ For this purpose, the `watch-events` property (`FileReadingMessageSource.setWatc
 With such an option, we can use one downstream flow logic for new files and use some other logic for modified files.
 The following example shows how to configure different logic for create and modify events in the same directory:
 
+It is worth mentioning that the `ENTRY_DELETE` event is involved in the rename operation of sub-directory of the watched directory.
+More specifically, `ENTRY_DELETE` event, which is related to the previous directory name, precedes `ENTRY_CREATE` event which notifies about the new (renamed) directory.
+On some operating systems (like Windows), the `ENTRY_DELETE` event has to be registered to deal with that situation.
+Otherwise, renaming watched sub-directory in the File Explorer could result in the new files not being detected in that sub-directory.
+
 ====
 [source,xml]
 ----