Constant branchless::git::TEST_ABORT_EXIT_CODE

pub const TEST_ABORT_EXIT_CODE: i32 = 127;

Similarly to INDETERMINATE_EXIT_CODE, this exit code is used officially by git-bisect and others to abort the process. It’s also typically raised by the shell when the command is not found, so it’s technically ambiguous whether the command existed or not. Nonetheless, it’s intuitive for a failure to run a given command to abort the process altogether, so it shouldn’t be too confusing in practice.