Linux support

Install dependencies for your distribution.

mkvtoolnix
kid3

Debian/Ubuntu based distribution(s):
sudo apt install kid3-cli mkvtoolnix

Solus:
sudo eopkg it kid3-cli mkvtoolnix

Install rmeta:

sudo wget -P /usr/bin https://raw.githubusercontent.com/HarveyDevel/rmeta/master/rmeta
Make sure the file has execute permissions:
sudo chmod +x /usr/bin/rmeta

Usage:

Please note this script will modify the metadata for ALL files in the active directory.

[command] [argument]
For mkv files:
rmeta mkv

For mp4 files:
rmeta mp4

For both mkv and mp4 files:
rmeta all

You can append -r to any rmeta command to modify files under each directory recursively:
rmeta all -r