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% Version Control Systems

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% Author: FOSSEE 

% Copyright (c) 2009, FOSSEE, IIT Bombay

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% Title page

\title[Version Control Systems]{SEES: Version Control Systems}

\author[FOSSEE] {FOSSEE}

\institute[IIT Bombay] {Department of Aerospace Engineering\\IIT Bombay}

\date[]{}

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\begin{document}

\begin{frame}

  \maketitle

\end{frame}

% CREATING TOC 

\begin{frame}

  \frametitle{Outline}

  \tableofcontents

  % You might wish to add the option [pausesections]

\end{frame}

%% There are some %$ used just to minimise the effect of $ sign used in lstlisting. In emacs it looks unhealthy.

% Introduction to course-need of version control, history, options available.

\section{Introduction}

\begin{frame}

  \frametitle{What is Version Control?}

  \begin{block}{From a blog post}

    ``Version control (or source control) is nothing more arcane than keeping copies of ones work as one make changes to it.''

  \end{block}

  \pause

  \begin{block}{}

    It is better to use these tools rather than wasting creativity to invent VCS which have files with names like \begin{color}{red}{prog1.py, prog2.py}\end{color} or \begin{color}{red}prog-old.py, prog.py.\end{color}

  \end{block}

\end{frame}

\begin{frame}

  \frametitle{Motivation behind such tools}

  \begin{itemize}

  \item Track the history and evolution of a program.

  \item To collaborate effectively on a project.

  \item \begin{color}{red}``To err is Human''\end{color} \pause for recovery we have ``Version Control''

  \end{itemize}

\end{frame}

%% Introduction to how logs are managed in VCS.

%% A analogy in logs and day-to-day life?

\begin{frame}[fragile]

  \frametitle{How does it work?}

  It can roughly be related to Computer/Video Games.

  \begin{itemize}

  \item We play games in stages.

  \item We pass a stage/task- \begin{color}{red}we SAVE the game.\end{color}

  \item We resume playing from there onwards.

  \item In-case we want to replay or revisit some particular stage, we start from position we saved earlier.

  \item Even we can change the course of play henceforth.

  \end{itemize}

\end{frame}

\begin{frame}[fragile]

  \frametitle{Better way to say:}

  \begin{center}

    \includegraphics[height=2.5in,width=2.5in, interpolate=true]{mario}

  \end{center}  

  \emphbar{VCS provides power to save and resume from a stage.}

\end{frame}

\begin{frame}

  \frametitle{How is it done?}

  \begin{itemize}

  \item It keeps track of changes you make to a file. You can improvise, revisit, and amend.

  \item All procedure is logged/recorded, so you and others can follow the development cycle.

  \end{itemize}  

\end{frame}

\begin{frame}

  \frametitle{Do we really need this?}

  \emphbar{For team of people working remotely(even different computers/machines) on a project, use of version control is inevitable!}

  \vspace{0.15in}

  \emphbar{For single person: managing projects and assignments becomes easy}

  \vspace{0.15in}

  \pause

  \emphbar{\color{red}{It is a good habit!}}

\end{frame}

\begin{frame}

  \frametitle{Whats on the menu!}

  \begin{itemize}

  \item cvs (Concurrent Version System)

  \item svn (Subversion)

  \item hg (Mercurial)

  \item bzr (Bazaar)

  \item git

  \end{itemize}

  \inctime{10}

\end{frame}

% Introduction to jargon 

\section{Learning the Lingo!}

\begin{frame}

  \frametitle{Common jargon: Basic setup}

  \begin{itemize}

  \item Repository(repo):\\

        The folder with all files.

  \item Server:\\

        Machine with main inventory/repo.

  \item Client:\\

        Local machines with copy of main repo.

  \end{itemize}

\end{frame}

\begin{frame}

  \frametitle{Actions}

  \begin{itemize}

  \item Add:\\

    Adding file into the repo for the first time.

  \item Version:\\

    Version number(Die Hard 4.0).

  \item Head/Tip:\\

    Most recent revision/stage.

  \item Check out/Clone:\\

    Initial download of working copy.

  \item Commit:\\

    Saving(recording) a change.

  \item Change log/History:\\

    List of all past changes.

  \end{itemize}

\end{frame}

\begin{frame}

  \frametitle{Actions cont...}

  \begin{itemize}

  \item Branch:\\

    Separate local copy for bug fixing, testing.

  \item Diff/Change:\\

    Changes made in a file in two different versions.

  \item Merge (or patch):\\

    Appling the changes to file, to make it up-to-date.

  \item Conflict:\\

    When merging a file is not obvious.

  \item Resolve:\\

    Fixing the conflict manually.

  \end{itemize}

\end{frame}

% Types of Version Controls

\section{Types of VCS}

\begin{frame}

  \frametitle{Types:}

  Based on ways of managing the repo there are two types of VCS:

  \begin{itemize}

  \item Centralized VCS\\

    cvs, svn fall under this category.

  \item Distributed VCS\\

    hg, bzr, git follows this methodology.

  \end{itemize}

  \emphbar{We would be covering \typ{hg}}

\end{frame}

\begin{frame}

  \frametitle{Why hg?}

    \includegraphics[height=.75in, interpolate=true]{mercurial}

  \begin{itemize}

  \item Easy to learn and use.

  \item Lightweight.

  \item Scales excellently.

  \item Written in Python.

  \end{itemize}

  \inctime{10}

\end{frame}

% Initializing the repo, cloning, committing changes, pushing, pulling to repo.

\section{Getting Started}

\begin{frame}[fragile]

  \frametitle{Getting comfortable:}

  For checking \typ{hg} installation and its version try:

  \begin{lstlisting}

    $ hg version    

  \end{lstlisting}

  To get broad help on \typ{hg} and commands available:

  \begin{lstlisting}

    $ man hg

    $ hg help

  \end{lstlisting}

  To get help on particular \typ{hg} related option try:

  \begin{lstlisting}

    $ hg help diff

  \end{lstlisting} %$

\end{frame}

\begin{frame}[fragile]

  \frametitle{Getting working/existing code base}

  \typ{clone} is used to make a copy of an existing repository. It can be both local or remote.

  \begin{lstlisting}

$ hg clone 

  http://hg.serpentine.com/tutorial/hello 

  localCopyhello

  \end{lstlisting}

  And we get a local copy of this repository. 

  \begin{lstlisting}

$ ls localCopyhello/

hello.c  Makefile

  \end{lstlisting}

\end{frame}

\begin{frame}[fragile]

  \frametitle{To start track-record on existing files}

  I have some files which I want to bring under version control. \typ{hg} provides \typ{init} command for this: 

  \begin{lstlisting}

$ ls -a circulate/

.  ..  lena.png  pendulum.txt  points.txt  pos.txt  sslc1.py  sslc1.txt

$ cd circulate/

$ hg init

$ ls -a

.  ..  .hg  lena.png  pendulum.txt  points.txt  pos.txt  sslc1.py  sslc1.txt    

  \end{lstlisting}

  \emphbar{\typ{.hg} directory keeps log of changes made henceforth.}

\end{frame}

\begin{frame}[fragile]

  \frametitle{Starting fresh}

  We can use \typ{init} to start a new repository also

  \begin{lstlisting}

$ mkdir Fevicol

$ cd Fevicol/

$ echo "print 'Yeh Fevicol ka majboot 

              jod hai'" > feviStick.py

$ ls -a

.  ..  feviStick.py

$ hg init

$ ls -a

.  ..  feviStick.py  .hg

  \end{lstlisting}

\end{frame}

\begin{frame}[fragile]

  \frametitle{Making copies: Branching}

  All \typ{hg} repositories are self-contained, and independent which can be copied(cloned):

  \begin{lstlisting}

$ hg clone localCopyhello newCopy

updating working directory

2 files updated, 0 files merged, 

0 files removed, 0 files unresolved

  \end{lstlisting}

  or

  \begin{lstlisting}

$ hg clone Fevicol Fevicol-pull

updating working directory

0 files updated, 0 files merged, 

0 files removed, 0 files unresolved

  \end{lstlisting}

  \inctime{20}

\end{frame}

%% Should we here stress on how are distribute VCS have 

%% different approach then centralized ones? Maybe a pic

%% or some other graphical representation.

\begin{frame}[fragile]

  \frametitle{Revisiting saved points:history/logs}

  In \typ{hg}, the difference between consecutive stages is termed as changeset.\\

  Once we have saved stages, we need a mechanism to review and access them, for that use \typ{log} command.

  \begin{lstlisting}

$ cd localCopyhello

$ hg log    

  \end{lstlisting}

\end{frame}

\begin{frame}[fragile]

  \frametitle{Understanding output}

  The output provides following information:

  \begin{itemize}

  \item changeset: Identifiers for the changeset.

  \item user: Person who created the changeset.

  \item date: Date and time of creation of changeset.

  \item summary: One line description.

  \end{itemize}

\end{frame}

\begin{frame}[fragile]

  \frametitle{History/Logs cont...}

  By default \typ{log} returns complete list of all changes. \\

  For selective view try:

\begin{lstlisting}

$ hg log -r 3

$ hg log -r 2:4

\end{lstlisting}

  tip/latest changes can be seen via:

  \begin{lstlisting}

$ hg tip    

  \end{lstlisting} %%$

  \inctime{5}

\end{frame}

\begin{frame}[fragile]

  \frametitle{Advancing through a stage:status}

  We often need to add/delete some files from directory(repo). The structure keeps on evolving, and tools for handling them are needed.\\

  We will use the Fevicol repo we created earlier.

  \begin{lstlisting}

$ cd Fevicol

$ hg log

$ hg st

? feviStick.py

  \end{lstlisting} %%$

  \typ{st} (aka status) is command to show changed files in the working directory.\\

\end{frame}

%% track record is confusing for some. Duma have some doubts :(

\begin{frame}[fragile]

  \frametitle{Adding files}

  "?" indicates that these file are aliens to track record.\\

  \typ{add} command is available to add new files to present structure.

  \begin{lstlisting}

$ hg add feviStick.py

$ hg st

A feviStick.py

  \end{lstlisting}

\end{frame}

\begin{frame}[fragile]

  \frametitle{Saving present stage: committing}

  \emphbar{This is equivalent to completing tasks, before reaching a stage where you want to save.}

  \typ{hg} uses \typ{ci}(aka \typ{commit}) command to save changes. So after adding file, we have to commit it also:

  \begin{lstlisting}

$ hg ci -u "Shantanu <shantanu@fossee.in>" 

        -m "First commit."

$ hg log

changeset:   0:84f5e91f4de1

tag:         tip

user:        Shantanu <shantanu@fossee.in>

date:        Fri Aug 21 23:37:13 2009 +0530

summary:     First commit.    

  \end{lstlisting}

\end{frame}

\begin{frame}[fragile]

  \frametitle{Other operations}

  \typ{hg} supports basic file-management functions like copy, remove, rename etc.

  \begin{lstlisting}

$ hg cp feviStick.py pidiLite.py

$ hg rename pidiLite.py feviCol.py

$ hg st

A feviCol.py

$ hg ci -u "Shantanu <shantanu@fossee.in>" 

        -m "Added feviCol.py."

$ hg tip| grep summary 

summary:     Added feviCol.py.

  \end{lstlisting} %$

%% Other commands which can be handy are \typ{remove}, \typ{revert} etc.

  \inctime{10}

\end{frame}

% Introduction to concepts of branches, merging patch?

\section{Sharing and Collaborating}

\begin{frame}[fragile]

  \frametitle{Distributing changes}

  \begin{itemize}

  \item All directory-structure(repo) are self-contained.

  \item Changes created are local.

    \begin{itemize}

    \item Until we sync. previously cloned repos.

    \end{itemize}

  \end{itemize}

  \begin{lstlisting}

$ hg pull 

pulling from /home/baali/Fevicol

requesting all changes

adding changesets

adding manifests

adding file changes

added 2 changesets with 2 changes to 2 files

(run 'hg update' to get a working copy)

  \end{lstlisting} %$

\end{frame}

\begin{frame}[fragile]

  \frametitle{Pulling changesets cont...}

  \typ{pull} command doesn't update current directory, it just imports changesets. To add all these changes, use \typ{up}:

  \begin{lstlisting}

$ cd Fevicol-pull

$ ls -a

.  ..  .hg

$ hg up

2 files updated, 0 files merged, 

0 files removed, 0 files unresolved

$ ls -a

.  ..  feviCol.py  feviStick.py  .hg    

  \end{lstlisting}

  \pause

  \emphbar{Why \typ{pull} and \typ{up} are needed separately?}

\end{frame}

\begin{frame}[fragile]

  \frametitle{Making changes across branches}

  \begin{lstlisting}

$ cd Fevicol-pull/

  \end{lstlisting} %$

  Lets edit and correct the feviStick.py 

\begin{lstlisting}

$ echo "print 'Ab no more Chip Chip'" 

        > feviStick.py

$ hg st

M feviStick.py

\end{lstlisting}

  'M' sign indicates that \typ{hg} has noticed change.\\

\end{frame}