New port: devel/grv: Terminal interface for viewing git repositories

Screenshot:
https://raw.githubusercontent.com/rgburke/grv/master/doc/grv-history-view.png

PR: 225617
Submitted by: Dmitri Goutnik <dg@syrec.org>
Approved by: adamw (mentor)
Differential Revision: https://reviews.freebsd.org/D14165