Almost finished slides on branching

branching/branching.tex

@@ -21,6 +21,22 @@
 
 \usetheme{lumc}
 
+\lstset{
+  basicstyle=\ttfamily,
+  language=none,
+  frame=none,
+  numbers=none,
+  numbersep=0
+}
+
+\AtBeginSection[]
+{
+  \begin{frame}
+    \frametitle{Table of contents}
+    \tableofcontents[currentsection]
+  \end{frame}
+}
+
 \begin{document}
 
 % This disables the \pause command, handy in the editing phase.
@@ -29,14 +45,15 @@
 % Make the title page.
 \bodytemplate
 
-% First page of the presentation.
+
 \section{The Git commit graph}
+
 \begin{frame}
   \frametitle{A linear history}
   \includegraphics[width=10cm]{images/linear}
   \begin{itemize}
-    \item Every commit has a parent
-    \item {\em Committing} creates a new commit on top of the current one
+    \item Every commit has a parent.
+    \item {\em Committing} creates a new commit on top of the current one.
   \end{itemize}
 \end{frame}
 
@@ -44,17 +61,17 @@
   \frametitle{The default \bt{master} branch}
   \includegraphics[width=10cm]{images/master}
   \begin{itemize}
-    \item A {\em branch} is a pointer to a commit
-    \item By default there is one branch: \bt{master}
+    \item A {\em branch} is a pointer to a commit.
+    \item By default there is one branch: \bt{master}.
   \end{itemize}
 \end{frame}
 
 \begin{frame}
   \frametitle{The current commit: \bt{HEAD}}
   \begin{itemize}
-    \item The current commit is called \bt{HEAD} (shown in blue)
-    \item \bt{HEAD} normally points to the current branch
-    \item Or to a commit if there is no current branch
+    \item The current commit is called \bt{HEAD} (shown in blue).
+    \item \bt{HEAD} normally points to the current branch.
+    \item Or to a commit if there is no current branch.
   \end{itemize}
   \vspace{1cm}
   \includegraphics[width=10cm]{images/head}
@@ -63,9 +80,9 @@
 \begin{frame}
   \frametitle{Committing moves \bt{HEAD} and the current branch}
   \begin{itemize}
-    \item Committing moves the current branch to the new commit
-    \item Of course, \bt{HEAD} moves with it
-    \item If there is no current branch, only \bt{HEAD} moves
+    \item Committing moves the current branch to the new commit.
+    \item Of course, \bt{HEAD} moves with it.
+    \item If there is no current branch, only \bt{HEAD} moves.
   \end{itemize}
   \vspace{1cm}
   \includegraphics[width=10cm]{images/commit}
@@ -75,16 +92,16 @@
   \frametitle{A non-linear history}
   \includegraphics[width=10cm]{images/nonlinear}
   \begin{itemize}
-    \item The commit graph can become non-linear
-    \item Usually by committing from the same commit twice
+    \item The commit graph can become non-linear.
+    \item Usually by committing from the same commit twice.
   \end{itemize}
 \end{frame}
 
 \begin{frame}
   \frametitle{Use branches to keep track of different code paths}
   \begin{itemize}
-    \item Branch names are easier to remember than commit hashes
-    \item Branch names make it clear what commits are about
+    \item Branch names are easier to remember than commit hashes.
+    \item Branch names make it clear what commits are about.
   \end{itemize}
   \vspace{0.5cm}
   \includegraphics[width=6cm]{images/branches}
@@ -93,44 +110,268 @@
 \begin{frame}
   \frametitle{Different code paths may later join}
   \begin{itemize}
-    \item Commits from different branches can be brought together
-    \item We call this {\em merging}
+    \item Commits from different branches can be brought together.
+    \item We call this {\em merging}.
   \end{itemize}
   \vspace{0.5cm}
   \includegraphics[width=6cm]{images/merge}
 \end{frame}
 
 
-\section{Managing branches}
+\section{Inspecting the commit graph}
+
+\begin{frame}
+  \frametitle{An example repository}
+  \includegraphics[width=8cm]{images/example}
+  \begin{itemize}
+    \item Branches \bt{license} and \bt{interface} diverged from \bt{master}.
+    \item Only \bt{license} has been merged back into \bt{master}.
+    \item Current branch is \bt{master}.
+  \end{itemize}
+\end{frame}
+
+\begin{frame}[fragile]
+  \frametitle{Showing the current branch: \bt{git status}}
+  \begin{lstlisting}
+$ git status
+# On branch master
+nothing to commit (working directory clean)
+  \end{lstlisting}
+  \bigskip
+  Remember: you cannot type \bt{git status} enough!
+\end{frame}
+
+\begin{frame}[fragile]
+  \frametitle{Listing branches: \bt{git branch}}
+  \begin{lstlisting}
+$ git branch
+  interface
+  license
+* master
+  \end{lstlisting}
+  \bigskip
+  Three branches, current branch is \bt{master}.
+  \pause
+  \bigskip
+  \begin{lstlisting}
+$ git branch -v
+  interface 8fc25c1 Trivial Python interface
+  license   0fbe3e3 Add MIT license
+* master    c7f3bd9 Add .gitignore file
+  \end{lstlisting}
+  \bigskip
+  \bt{-v}: Shows the commit each branch points to.
+\end{frame}
+
+\begin{frame}[fragile]
+  \frametitle{The commit log: \bt{git log}}
+  \begin{lstlisting}
+$ git log --oneline --decorate
+c7f3bd9 (HEAD, master) Add .gitignore file
+4a44c4e Merge branch 'license'
+64af1ee Add course teachers to README
+0fbe3e3 (license) Add MIT license
+d1c7fd7 Initial commit with README
+  \end{lstlisting}
+  \bigskip
+  \bt{--oneline}: Shows commit summary on one line.
+
+  \bt{--decorate}: Adds branch information.
+\end{frame}
+
+\begin{frame}[fragile]
+  \frametitle{The commit log as a graph: \bt{git log}}
+  \begin{lstlisting}
+$ git log --oneline --decorate --graph --all
+* 8fc25c1 (interface) Trivial Python interface
+| * c7f3bd9 (HEAD, master) Add .gitignore file
+|/
+*   4a44c4e Merge branch 'license'
+|\
+| * 0fbe3e3 (license) Add MIT license
+* | 64af1ee Add course teachers to README
+|/
+* d1c7fd7 Initial commit with README
+  \end{lstlisting}
+  \bigskip
+  \bt{--graph}: Shows the commit graph.
 
-% todo: listing branches, showing current branch
+  \bt{--all}: Includes all branches instead of just the current.
+\end{frame}
 
 \begin{frame}[fragile]
   \frametitle{Switching to another branch: \bt{git checkout}}
-  \begin{lstlisting}[language=none]
-    git checkout mybranch
+  \begin{lstlisting}
+$ git checkout interface
+Switched to branch 'interface'
+  \end{lstlisting}
+  \bigskip
+  This points \bt{HEAD} to the named branch and updates your working
+  directory.
+  \pause
+  \bigskip
+  \begin{lstlisting}
+$ git status
+# On branch interface
+nothing to commit (working directory clean)
   \end{lstlisting}
+\end{frame}
+
+
+\section{Manipulating the commit graph}
+
+\begin{frame}
+  \frametitle{An example repository}
+  \includegraphics[width=8cm]{images/example}
   \begin{itemize}
-    \item Makes \bt{mybranch} the current branch (and moves \bt{HEAD})
+    \item Branches \bt{license} and \bt{interface} diverged from \bt{master}.
+    \item Only \bt{license} has been merged back into \bt{master}.
+    \item Current branch is \bt{master}.
   \end{itemize}
-  \vspace{0.5cm}
-  \includegraphics[width=10cm]{images/checkout}
 \end{frame}
 
 \begin{frame}[fragile]
   \frametitle{Creating a new branch: \bt{git branch}}
-  \begin{lstlisting}[language=none]
-    git branch mybranch
+  \begin{lstlisting}
+$ git branch lib
+  \end{lstlisting}
+  \bigskip
+  Creates branch \bt{lib} at \bt{HEAD}.
+  \pause
+  \bigskip
+  \begin{lstlisting}
+$ git checkout lib
+Switched to branch 'lib'
+  \end{lstlisting}
+  \pause
+  \bigskip
+  Or, for Git pro's, in one command:
+  \bigskip
+  \begin{lstlisting}
+$ git checkout -b lib
+Switched to a new branch 'lib'
+  \end{lstlisting}
+  \bigskip
+  At this point, \bt{lib} is just a label to the same commit as \bt{master}.
+\end{frame}
+
+\begin{frame}
+  \frametitle{Our example repository}
+  \includegraphics[width=8cm]{images/example-branched}\\
+  \vspace{0.5cm}
+  Created branch \bt{lib} from \bt{master}.
+\end{frame}
+
+\begin{frame}[fragile]
+  \frametitle{Working on a branch: \bt{git commit}}
+  We can extend the \bt{lib} branch by adding commits.
+  \bigskip
+  \begin{lstlisting}
+$ echo 'VERSION=1' > testlib.py
+$ git add testlib.py
+$ git commit -m 'Add empty testlib'
+  \end{lstlisting}
+  \pause
+  \bigskip
+  \begin{lstlisting}
+$ git log --oneline --decorate --graph --all
+* 251a51b (HEAD, lib) Add empty testlib
+* c7f3bd9 (master) Add .gitignore file
+| * 8fc25c1 (interface) Trivial Python interface
+|/
+*   4a44c4e Merge branch 'license'
+|\
+| * 0fbe3e3 (license) Add MIT license
+...
+  \end{lstlisting}
+\end{frame}
+
+\begin{frame}
+  \frametitle{Our example repository}
+  \includegraphics[width=8cm]{images/example-committed}\\
+  \vspace{0.5cm}
+  Extended branch \bt{lib}.
+\end{frame}
+
+\begin{frame}[fragile]
+  \frametitle{Fast forward merging: \bt{git merge}}
+  Let's merge our work on \bt{lib} back into \bt{master}.
+  \bigskip
+  \begin{lstlisting}
+$ git checkout master
+Switched to branch 'master'
+$ git merge lib
+Updating c7f3bd9..251a51b
+Fast-forward
+ testlib.py |    1 +
+ 1 file changed, 1 insertion(+)
+ create mode 100644 testlib.py
+  \end{lstlisting}
+  \bigskip
+  This merge was easy:
+  \begin{itemize}
+    \item \bt{lib} was directly upstream of \bt{master}.
+    \item Git just moves \bt{HEAD} and \bt{master} to point to \bt{lib}.
+    \item This is called a {\em fast forward merge}.
+  \end{itemize}
+\end{frame}
+
+\begin{frame}
+  \frametitle{Our example repository}
+  \includegraphics[width=8cm]{images/example-merged-ff}\\
+  \vspace{0.5cm}
+  Merged branch \bt{lib} into \bt{master} (fast forward).
+\end{frame}
+
+\begin{frame}[fragile]
+  \frametitle{Three-way merging: \bt{git merge}}
+  Let's merge our work on \bt{interface} back into \bt{master}.
+  \bigskip
+  \begin{lstlisting}
+$ git merge interface
+Merge made by the 'recursive' strategy.
+ interface.py |    3 +++
+ 1 file changed, 3 insertions(+)
+ create mode 100755 interface.py
   \end{lstlisting}
+  \bigskip
+  This merge was harder:
   \begin{itemize}
-    \item Creates branch \bt{mybranch} at \bt{HEAD}
-    \item But doesn't switch to it! (use \bt{git checkout})
+    \item \bt{interface} and \bt{master} had diverged.
+    \item Git determines changes in \bt{interface} and \bt{master} since their
+      most recent common ancestor and creates a new commit from that.
+    \item This is called a {\em recursive three-way merge} and the resulting
+      merge a {\em merge commit}.
   \end{itemize}
+\end{frame}
+
+\begin{frame}
+  \frametitle{Our example repository}
+  \includegraphics[width=8cm]{images/example-merged}\\
   \vspace{0.5cm}
-  \includegraphics[width=10cm]{images/branch}
+  Merged branch \bt{interface} into \bt{master}.
+\end{frame}
+
+\begin{frame}[fragile]
+  \frametitle{Deleting branches: \bt{git branch}}
+  Old branches that have been merged can be deleted.
+  \bigskip
+  \begin{lstlisting}
+$ git branch -d interface
+Deleted branch interface (was 8fc25c1).
+  \end{lstlisting}
+  \bigskip
+  \begin{lstlisting}
+$ git branch -d lib license
+Deleted branch lib (was 251a51b).
+Deleted branch license (was 0fbe3e3).
+  \end{lstlisting}
+  \bigskip
+  No history is lost, just labels removed.
 \end{frame}
 
-% todo: merging branches, tags
+
+% todo: basic merge conflicts, tags
 
 
 \section{Questions?}