Packmule is a tool designed to assist in Minecraft addon (.MCPACK, .MCWORLD) development by making it easy to transfer behavior pack, resource pack, and world files between a folder such as a git repository and the game directory.
Packmule's workflow revolves around 'Pack Hubs' (windows inside the program). They are representations of the addons present in any given file directory. Pack Hubs can be created with the File menu or with the ctrl + n shortcut. When a directory is entered into the textbox at the bottom of a Pack hub, it will be searched for valid behavior packs, resource packs, and minecraft worlds. These packs/worlds will populate a listbox in the Packhub and can be deleted with the large red button or copied to the target hub with the green button.
My usual setup. A hub for my repository, com.mojang folder, and a backup directory just in case.