Add introduction subsections

The note slides would otherwise have a blank line where the subsection
would be for these introduction slides.

Author: jmbtutor

understanding-git.tex

@@ -133,6 +133,7 @@ \section{Introduction}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \section{Commits}
+\subsection{Introduction}
 
 \begin{frame}
   \frametitle{What is a commit?}
@@ -351,6 +352,7 @@ \subsection{\gitcmd{cherry-pick}}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \section{Branches}
+\subsection{Introduction}
 
 \begin{frame}
   \frametitle{What is a branch?}
@@ -1134,6 +1136,7 @@ \subsection{\gitcmd{merge}}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \section{Remote Repositories}
+\subsection{Introduction}
 
 \begin{frame}
   \frametitle{What are remote repositories?}