Quite literally 10 min ago Ivy just made another unstable patch with the clashing.
Also. Cowboy bullets now collide if 2 of them shoot each other at the same time

0.6.12-unstable
– New system: clashing
– Melee attacks that hit each other will trigger a clash animation. This pushes the players back, and causes both players to become actionable immediately. This clash only occurs if both hitboxes are close enough in damage (within 600 points) or neither hitbox hits the other character’s hurtbox. Otherwise these attacks will trade like normal.