The following MWE will work on 3.7 but not 3.8rc4: ```cmake cmake_minimum_required(VERSION 3.7.0) project(Foo) include(ExternalProject) ExternalProject_Add(gitTest GIT_REPOSITORY https://github.com/githubtraining/hellogitworld.git GIT_TAG bisect CONFIGURE_COMMAND "" BUILD_COMMAND echo "Built" INSTALL_COMMAND "" TEST_COMMAND "" ) ``` The problem is the addition of `--` after the branch name in the git checkout command in `gitTest-prefix/tmp/gitTest-gitclone.cmake` only in 3.8; this is trying to be smart and not clash with a file name, but it also changes the behavior of the git command when you are trying to get a branch that does not exist locally in your cloned repository (i.e., any branch other than master). In this case, `git checkout bisect` works as expected but `git checkout bisect --` fails miserably because `bisect` doesn't refer to a local branch. (I don't like that git behavior personally, but that's the way it works)