I'm very glad GuiShop is open-source, because it encourages collaboration to improve the plugin and makes adding custom features easy.

That said, there are a few problems my IDE and maven report after cloning and building the source:

1. The section sign ('§') is replaced with a broken character, '�', when I initially clone the repository. However, if one conducts a find and replace for all '�' with '§', git reports a diff and wants the changes to be committed. Note that the characters are not changed when forking but when cloning the repo.
2. Because the .classpath references libraries on your personal computer (e.g. "C:/Users/Bryce/Desktop/1.15.2/plugins/Vault.jar") the project initially fails to build. This can be solved by removing the .classpath references, which are unnecessary because maven already resolves all dependencies. However, again it results in a git diff.
3. There are 2 IDE errors related to the same construct. There's a comment describing the lines: "Use for comment injection method for forward & backward compat". I'm not sure what this means or how to solve it, but I do know that it makes Eclipse angry. (Quantity.java:110 and Shop.java:234)

I can make a PR to fix problem 1 and problem 2, but I don't know what to do for problem 3.

I will look into these issues for 7.3.9's release. Thanks for the report!