According to the documentation [merge] is for Layers to output a single image.
Has this changed? I use this so I can keep my lines, colors, shadows and highlights separate in the PSD file. This way I can easily go back and edit the layers for tweaking the look of a character after the fact but still maintaining shape and size.
From the https://github.com/EsotericSoftware/spine-scripts/tree/master/photoshop page:
[merge] Layers in the group are merged and a single image is output.
I am using ex. tag structure Layer Group Names:
[merge] Upper Body
[merge] Lower Body
When I run the old script each group is merged into one image named <Group Name>.png. (Ex. Head.png) With the new script they are merged and named as undefined.png over and over each time overwriting the last merged image.