CURLFTP_CREATE_DIR, libcurl will attempt to create any remote directory that it fails to "move" into.
For FTP requests, that means a CWD command fails. CWD being the command that changes working directory.
For SFTP requests, libcurl will attempt to create the remote directory if it can't obtain a handle to the target-location. The creation will fail if a file of the same name as the directory to create already exists or lack of permissions prevents creation.
CURLFTP_CREATE_DIR_RETRY, tells libcurl to
retry the CWD command again if the subsequent MKD command fails. This is
especially useful if you're doing many simultaneous connections against the
same server and they all have this option enabled, as then CWD may first fail
but then another connection does MKD before this connection and thus MKD fails
but trying CWD works!