dot_clean -- Merge ._* files with corresponding native files

When you copy certain macOS files to a non-HFS+/APFS formatted disk (such as a file share), the metadata will be extracted from the files and put in invisible files starting with `._`.

This can leads to issues or can look garbage when you send these files to Git.

According to Apple: 

Before Mac OS X, the Mac OS used ‘forked’ files, which have two components: a data fork and a resource fork. The Mac OS Standard (HFS) and Mac OS Extended (HFS Plus) disk formats support forked files. When you move these types of files to other disk formats, the resource fork can be lost.

With Mac OS X, there is a mechanism called “Apple Double” that allows the system to work with disk formats that do not have a forked file feature, such as remote NFS, SMB, WebDAV directories, or local UFS volumes. Apple Double does this by converting the file into two separate files. The first new file keeps the original name and contains the data fork of the original file. The second new file has the name of the original file prefixed by a “._ “ and contains the resource fork of the original file. If you see both files, the ._ file can be safely ignored. Sometimes when deleting a file, the ._ component will not be deleted. If this occurs you can safely delete the ._ file.

I'm don't necessarily agree that deleting them is harmless. I've seen cases where doing so would create issues. Last time I remember was while I was an assistant editor for a feature film. I did an rsync and forgot the -E flag. All the asset files lost their metadata and I had to reimport all  manually in Final Cut Pro.

An easy way to fix this is to run the `dot_clean` command, available from the optional Command Line Tools.

dot_clean /Users/fti/Git/SplashBuddy