Unified Diff Mode Toggle

Thanks to @markdorison 🙏🏽 diffnav now supports toggling between side-by-side and unified diff modes.
Press s to switch between the two or use the --side-by-side and --unified flags.
You can also set this in the config file under ui.sideBySide.

Changelog

• 4bfcf87 feat: add unified diff view option (#63)