问题
What do these settings actually do?
What values should a pro have on these and what impact do they have? Refactoring undo for instance, "X file has already changed so you can not undo" would be GREAT if we could throw in the garbage using any setting combination.
回答1:
Based on this question the documentUndoLimit is the max level of undo for each document (actually current document) and the globalUndoLimit is the undo max level of undo for the IDE on the current project.
For example, when you change codes of a file and then decide to undo the documentUndoLimit value is the number of levels that you can go back. but when you add some files or delete some other files, rename them and etc, the globalUndoLimit value is the number of levels that you can go back.
来源：https://stackoverflow.com/questions/59423614/explanation-of-intellij-undo-documentundolimit-and-undo-globalundolimit