Implement aborting of games on engine request.

A new game-end command is added. For bakward compatibility it is disguised
as an old one, namely "1/2-1/2 {Engine Abort Request}". These resultDetails
are recognized as special, and rather than ending the game in a draw (which
GUIs not implementing this), the game will be completely 'expunged' from
the match or tourney it is part of, leaving no trace in the saveGameFile.

diff --git a/backend.c b/backend.c
index 25134bf..3ab07f9 100644 (file)
--- a/backend.c
+++ b/backend.c
@@ -10632,6 +10632,10 @@ GameEnds (ChessMove result, char *resultDetails, int whosays)
                       resultDetails = buf;
                 }
                 /* (Claiming a loss is accepted no questions asked!) */
+           } else if(matchMode && result == GameIsDrawn && !strcmp(resultDetails, "Engine Abort Request")) {
+               forwardMostMove = backwardMostMove; // [HGM] delete game to surpress saving
+               result = GameUnfinished;
+               if(!*appData.tourneyFile) matchGame--; // replay even in plain match
            }
            /* [HGM] bare: don't allow bare King to win */
            if((gameInfo.holdingsWidth == 0 || gameInfo.variant == VariantSuper