add id to h4. default branch name

Author: noureddin

book/01-introduction/sections/first-time-setup.asc

@@ -84,6 +84,7 @@ You may find, if you don't setup your editor like this, you get into a really co
 An example on a Windows system may include a prematurely terminated Git operation during a Git initiated edit.
 ====
 
+[[_default_branch]]
 ==== Your default branch name
 
 By default Git will create a branch called _master_ when you create a new repository with `git init`.