I have two cloned repositories of two very similar open-source projects, which I have been working on in different instances in Sublime Text 2 to arrive at my desired result. Co
The Diff Option only appears if the files are in a folder that is part of a Project.
Than you can actually compare files natively right in Sublime Text.
Navigate to the folder containing them through Open Folder... or in a project Select the two files (ie, by holding Ctrl on Windows or ⌘ on macOS) you want to compare in the sidebar Right click and select the Diff files... option.