Add "git --checkout -- ." command

basics/basics.tex

@@ -187,6 +187,43 @@
   \end{lstlisting}
 \end{frame}
 
+\begin{frame}[fragile]
+  \frametitle{Undoing changes.}
+
+  Keep in mind that ``\bt{git reset}'' by default sets a staged file back to unstaged.
+  \begin{lstlisting}[language=none, caption=Unstage a file.]
+    $ git reset README
+    $ git status
+    # Changes not staged for commit:
+    #       modified:   README
+  \end{lstlisting}
+  \bigskip
+  \pause
+
+  To discard all changes in an unstaged file, you can use ``\bt{git checkout}''
+  \begin{lstlisting}[language=none, caption=Discarding changes.]
+    $ git checkout -- .
+    $ git status
+    nothing to commit, working directory clean
+  \end{lstlisting}
+  
+\end{frame}
+
+\begin{frame}[fragile]
+  \frametitle{Undoing changes.}
+
+  For now, let's commit our change and move on.
+  \bigskip
+
+  \begin{lstlisting}[language=none, caption=Adding a new version of a file.]
+    $ echo Second version. > README
+    $ git commit
+    $ git status
+    nothing to commit, working directory clean
+  \end{lstlisting}
+  \bigskip
+\end{frame}
+
 \begin{frame}[fragile]
   \frametitle{Viewing the history.}