JIRA: https://jira.spring.io/browse/INT-4232
Currently to implement the synchronization logic when remote file is modified there is only one way: remove local file and provide a `localFilter` which can be clear from the removed file as well.
The Reference Manual claims that `FileSystemPersistentAcceptOnceFileListFilter` can let us pick up a fresh version of the remote file if we configure `preserveTimestamp = true`, but actually `AbstractInboundFileSynchronizer` just bypass that logic because it check a local file for existence.
* Modify `AbstractInboundFileSynchronizer` to compare `lastModified` of the remote file with local version if `preserveTimestamp == true`
* Also replace `AcceptOnceFileListFilter` to the `FileSystemPersistentAcceptOnceFileListFilter` since the first one doesn't care about `lastModified`.
If `preserveTimestamp` isn't in use the `FileSystemPersistentAcceptOnceFileListFilter` works fully similar to the `AcceptOnceFileListFilter`
**Cherry-pick to 4.3.x except test-case**
Make `SftpStreamingMessageSourceTests` compatible with Windows
Looks like SFTP embedded server provides different permissions for files on different OSs
Doc Polishing
Conflicts:
spring-integration-file/src/test/java/org/springframework/integration/file/remote/synchronizer/AbstractRemoteFileSynchronizerTests.java
spring-integration-ftp/src/test/java/org/springframework/integration/ftp/dsl/FtpTests.java
spring-integration-sftp/src/test/java/org/springframework/integration/sftp/inbound/SftpStreamingMessageSourceTests.java
src/reference/asciidoc/whats-new.adoc
Resolved.
909060abd5