fix: negate followLinks flag for checkSymlinkState

[bemoty]

I'm using sshd-sftp as a custom SFTP server for its great virtual file system capabilities (it allows me to easily create a virtual space for each user). Each user directory contains symlinks (essentially "shares") to folders outside of the virtual file system.

After upgrading to 2.16.0 I noticed that file deletion did not work anymore. It kept giving me a NoSuchFileException "Removal candidate not found".

In doRemoveFile it seems like followLinks is missing a ! before being passed to checkSymlinkState. This was done correctly in other methods such as doRemoveDirectory.

[tomaswolf]

Good catch!

Looking through the callers of checkSymlinkState it appears that it is also wrong at

mina-sshd/sshd-sftp/src/main/java/org/apache/sshd/sftp/server/SftpSubsystem.java

Line 848 in 2bb67e6

return resolveFileAttributes(file, flags, followLinks, options);

Can we also add tests for this (at least on Unix-like platforms, where we have symlinks)?

[bemoty]

I gave it a try! Not sure if this was the right place for them though... let me know if you need me to move something. I created one test case for each checkSymlinkState caller, and excluded Win32 from the tests.

[tomaswolf]

Thanks a lot for the fixes and tests!