Help: diff-command
Bounty program for improvements to Tcl and certain Tcl packages.
Tcl 2019 Conference, Houston/TX, US, Nov 4-8
Send your abstracts to tclconference@googlegroups.com
or submit via the online form by Sep 9.

The "diff-command" setting:

The value is an external command to run when performing a diff. If undefined, the internal text diff will be used.