Help: gmerge-command
Bounty program for improvements to Tcl and certain Tcl packages.

The "gmerge-command" setting:

The value is a graphical merge conflict resolver command operating on four files. Examples:
kdiff3 "%baseline" "%original" "%merge" -o "%output"
xxdiff "%original" "%baseline" "%merge" -M "%output"
meld "%baseline" "%original" "%merge" --output "%output"