Delta provides language syntax-highlighting, within-line insertion/deletion detection, and restructured diff output for git on the command line.
Found via https://tecosaur.github.io/emacs-config/config.html
There are other programs using the name delta, for example
https://guix.gnu.org/packages/delta-2006.08.03/
"Delta assists you in minimizing "interesting" files subject to a test of their interestingness."