carthage buildafter changing framework code? if so, almost no time saving. OK so I will try changing something in a framework and see whether it updates without reruning
bootstrapinstead. carthage bootstrap is similar to update but it's working on Cartfile.resolved as opposed to Cartfile.
--use-submodulesoption adds each dependency in the Checkouts folder to your Git repository as a submodule, meaning you can change the dependencies’ source, and commit and push those changes elsewhere without fear of an overwrite.