Add html escaping for default branch name

This escapes html chars for default branch
name value in initializing repository instructions

This is to prevent XSS vulnerability

Changelog: security

app/views/projects/empty.html.haml

@@ -44,26 +44,26 @@
           :preserve
             git clone #{ content_tag(:span, default_url_to_repo, class: 'js-clone')}
             cd #{h @project.path}
-            git switch -c #{default_branch_name}
+            git switch -c #{h default_branch_name}
             touch README.md
             git add README.md
             git commit -m "add README"
           - if @project.can_current_user_push_to_default_branch?
             %span><
-              git push -u origin #{ default_branch_name }
+              git push -u origin #{h default_branch_name }
 
       %fieldset
         %h5= _('Push an existing folder')
         %pre.bg-light
           :preserve
             cd existing_folder
-            git init --initial-branch=#{default_branch_name}
+            git init --initial-branch=#{h default_branch_name}
             git remote add origin #{ content_tag(:span, default_url_to_repo, class: 'js-clone')}
             git add .
             git commit -m "Initial commit"
           - if @project.can_current_user_push_to_default_branch?
             %span><
-              git push -u origin #{ default_branch_name }
+              git push -u origin #{h default_branch_name }
 
       %fieldset
         %h5= _('Push an existing Git repository')