Use the progit.asc root document for the books
Use the progit.asc root document for the books

Using the progit allows for the migration of the book's files layout
needed by the new asciidoctor 1.5 versions.

git/git-scm.com,Mokolea/git-scm.com,mosoft521/gitscm-next,mosoft521/gitscm-next,git/git-scm.com,jasonlong/git-scm.com,jasonlong/git-scm.com,Mokolea/git-scm.com,git/git-scm.com,Mokolea/git-scm.com,Mokolea/git-scm.com,mosoft521/gitscm-next,jasonlong/git-scm.com,jasonlong/git-scm.com,git/git-scm.com,mosoft521/gitscm-next