Add illustrations to section pages

An illustration with the default repo (with a remote repository added)
was added to each section page. The parts that are not the focus for the
section are faded (e.g. for the Commits section, branches are faded).

gitdags was modified to include a "fade" style and new commands
`\gitbranchfade`, `\gitremotebranchfade` and `\gittagfade`.

Author: jmbtutor

gitdags.sty

@@ -184,6 +184,11 @@
     align          = left,
     font           = \ttfamily\tiny,
   },
+  fade/.style={
+    reset preaction,
+    draw opacity = .25,
+    fill opacity = .25,
+  },
 }
 
 % directed acyclic graph
@@ -205,6 +210,19 @@
   \draw[DAGrefedge] (#4) -- (\nodename@gitdags);
 }
 
+\newcommand\gitbranchfade[4][]{%
+  \renewcommand\nodename@gitdags{#1}%
+  \if\relax\detokenize{#1}\relax% check for empty optional argument
+    \renewcommand\nodename@gitdags{#2}%
+  \fi
+  \node[
+    DAGref,
+    fade,
+    fill = yellow!30,
+  ] (\nodename@gitdags) [#3] {#2};
+  \draw[DAGrefedge, fade] (#4) -- (\nodename@gitdags);
+}
+
 % remote-branch reference
 \newcommand\gitremotebranch[4][]{%
   \renewcommand\nodename@gitdags{#1}%
@@ -218,6 +236,19 @@
   \draw[DAGrefedge] (#4) -- (\nodename@gitdags);
 }
 
+\newcommand\gitremotebranchfade[4][]{%
+  \renewcommand\nodename@gitdags{#1}%
+  \if\relax\detokenize{#1}\relax% check for empty optional argument
+    \renewcommand\nodename@gitdags{#2}%
+  \fi
+  \node[
+    DAGref,
+    fade,
+    fill = solarized-blue!20,
+  ] (\nodename@gitdags) [#3] {#2};
+  \draw[DAGrefedge, fade] (#4) -- (\nodename@gitdags);
+}
+
 % tag reference
 \newcommand\gittag[4][]{%
   \renewcommand\nodename@gitdags{#1}%
@@ -231,6 +262,19 @@
   \draw[DAGrefedge] (#4) -- (\nodename@gitdags);
 }
 
+\newcommand\gittagfade[4][]{%
+  \renewcommand\nodename@gitdags{#1}%
+  \if\relax\detokenize{#1}\relax% check for empty optional argument
+    \renewcommand\nodename@gitdags{#2}%
+  \fi
+  \node[
+    DAGref,
+    fade,
+    fill = solarized-magenta!20,
+  ] (\nodename@gitdags) [#3] {#2};
+  \draw[DAGrefedge, fade] (#4) -- (\nodename@gitdags);
+}
+
 % HEAD symbolic reference
 \newcommand\gitHEAD[2]{%
   \node[

understanding-git.tex

@@ -153,7 +153,27 @@ \section{Introduction}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \section{Commits}
-\frame{\sectionpage}
+\begin{frame}
+  \sectionpage
+  \begin{figure}
+    \centering
+    \begin{tikzpicture}
+      \gitDAG{
+        A -- B -- {
+          D,
+          C -- E
+        }
+      };
+      \gitbranchfade{master}
+      {above=of D} {D}
+      \gitremotebranchfade{origin/master}
+      {right=of master} {D}
+      \gitbranchfade{topic}
+      {above=of E} {E}
+    \end{tikzpicture}
+  \end{figure}
+\end{frame}
+
 \subsection{Introduction}
 
 \begin{frame}
@@ -559,7 +579,27 @@ \subsection{\gitcmd{revert}}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \section{Branches}
-\frame{\sectionpage}
+\begin{frame}
+  \sectionpage
+  \begin{figure}
+    \centering
+    \begin{tikzpicture}
+      \gitDAG{[nodes=unreachable]
+        A -- B -- {
+          D,
+          C -- E
+        }
+      };
+      \gitbranch{master}
+      {above=of D} {D}
+      \gitremotebranchfade{origin/master}
+      {right=of master} {D}
+      \gitbranch{topic}
+      {above=of E} {E}
+    \end{tikzpicture}
+  \end{figure}
+\end{frame}
+
 \subsection{Introduction}
 
 \begin{frame}
@@ -1377,7 +1417,26 @@ \subsection{\gitcmd{merge}}
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 \section{Remote Repositories}
-\frame{\sectionpage}
+\begin{frame}
+  \sectionpage
+  \begin{figure}
+    \centering
+    \begin{tikzpicture}
+      \gitDAG{[nodes=unreachable]
+        A -- B -- {
+          D,
+          C -- E
+        }
+      };
+      \gitbranchfade{master}
+      {above=of D} {D}
+      \gitremotebranch{origin/master}
+      {right=of master} {D}
+      \gitbranchfade{topic}
+      {above=of E} {E}
+    \end{tikzpicture}
+  \end{figure}
+\end{frame}
 \subsection{Introduction}
 
 \begin{frame}