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: 

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.