Here is a little thought about th unique path issue,
I think it should just let user to specify the image folder to use when they manually editing the attachment path. Just like visiting a index.htm file on any website, user obviously need to tell which domain they want to load whether it is google.com or esotericsoftware.com.
In theory, user generally don't need to touch it as images are imported by default and just being dragged from the image tree to the canvas which the image folder is implicitly known when being dragged.
The image folder selection UI and image path prefix can also be hidden when not using multiple image folders. Just like how you hided the "default" skin when skin is not used in a project.
when multiple image folder NOT used:
-head.png
(the complete abs path could be "images/head.png" internally which is transparent to user)
when multiple image folder is used:
-[shared] / head.png
-[images] / head.png
where [] maybe presented as a drop down for user to change in an attachment.
For simplicity, a rule can be made to prevent image folders to have the same name.
Say default folder is called "images", additional image folder can no longer be called images.
If user want to use "c:/workspace/spine/shared/images" as secondary folder, need to rename it to something like "c:/workspace/spine/shared_images" to avoid same name issue.
The thing that could be a problem is that those entries under the skeleton tree seems always need a unique name which I quite don't understand as a programmer because all of them are unique by their full path under the tree.
Example:
root/body_part1/eye
root/body_part2/eye << this is forbidden because bone eye already exist.
but they can be identified correctly with full path...
This unique file name limitation could cause problem when multiple image folders having file with the same name.
Anyway, thanks for creating an issue for this improvement.
I would be find without this feature but I do like contribute my thought to help development goes in the right direction especially for feature that could improve my workflow so pardon me if I typed too much on this subject.
