gametree-half-ply-regexp

gametree-half-ply-regexp is a variable defined in `gametree.el'.
Its value is

":"

Documentation:
Matches ends of numbers of moves by the "second" player.
For instance, it is an almost universal convention in chess to postfix
numbers of moves by Black (if considered in isolation) by the ellipsis
"...". This is NOT a good choice for this program, though, because it
conflicts with the use of ellipsis by Outline mode to denote collapsed
subtrees. The author uses ":" because it agrees nicely with a set of
LaTeX macros he uses for typesetting annotated games.

You can customize this variable.