merge folder trees on OSX by moving, not copying them
Have you tried DiffMerge ? Its an application that is used to merge and compare files and folders.

It updates the content of respective folders by comparing and merging contents graphically.

Product Features

DiffMerge is an application to visually compare and merge files on Windows, OS X and Linux.

Graphically shows the changes between two files. Includes intra-line highlighting and full support for editing.

Graphically shows the changes between 3 files. Allows automatic merging (when safe to do so) and full control over editing the resulting file.

Performs a side-by-side comparison of 2 folders, showing which files are only present in one file or the other, as well as file pairs which are identical or different.

Right-click on any two files in Windows Explorer to diff them immediately.

Rulesets and options provide for customized appearance and behavior.

Identical feature set on Windows, OS X, and Linux.