.. Prerequisites
.. -------------

.. None

.. Author : Primal Pappachan
   Internal Reviewer : Kiran Isukapatla
   Date: Jan 8, 2012
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Script
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{{{ Show the first slide containing title, name of the production team along with the logo of MHRD}}}

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Hello friends and welcome to the tutorial on 'Version Control with Hg' 

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{{{Show the slide containing the objectives}}}

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At the end of this tutorial you will be able to

1. Understand what is Version Control and the need for it.

#. Create and use a repository on a daily basis.

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First, let's understand what 'Version Control' is.

.. L3

{{{Show the slide 'what is version control'}}}

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'Version control' is a way to track files over time and share them. This allows access to earlier versions of a file(s) if and when required. It therefore enables us to make changes to the content of a file, view it's change log and collaborate on a single piece of work with a team of people.
 

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{{{Show the slide 'Home-brewed'}}}

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Let's look at an example of home-brew Version Control system

Version control is a way of backing up files, before making changes. Most people would have cooked up their own version control system, without realizing, there were tools built by others, that performs the task in a more organized and systematic way.  

.. L5

{{{Show the slide 'Problems'}}}

Let's look at the various problems associated with this set-up.

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Now, let's move to identifying the needs for a 'Version Control System'.

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{{{Show the slide 'The need for Version Control'}}}

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We have seen that one of the main motivations to use a Version Control system is the ability to go back to a working version of a file, when something goes wrong. Below are a few more advantages of using an automated version control system.

1. By tracking the history of a project, any person may see the evolution of a project.

#. Allows for effective collaboration on a project, as everything is shared.

#. Helps to identify which additions have broken down a project and thus aids in efficient tracking down of the bugs.

#. It is good for a one man show as it is for a big group of people working on a project.


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{{{Show the slide 'How does it work? - Analogy}}}

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It is, in some ways, similar to playing a video game. We generally play games in stages. While playing, we save the game at some instances as per our choice. We continue playing, but we could, if necessary, choose to go back to one of the saved states and start over. In this manner, we could change the state of the game.

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{{{Show the slide 'Mercurial or hg'}}}

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Some of the Version Control tools available and used widely are:

1. cvs(Concurrent Version Systems)
	
#. svn(subversion)

#. hg(mercurial)

#. git

.. R10

Each of these tools have their own merits and demerits. In this tutorial we shall learn how to use mercurial or hg.

Let's now get into Installation

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sudo apt-get install mercurial

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For Windows,

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http://mercurial.selenic.com/downloads/

Type 'hg' which lists out all the commands 

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$hg

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and 'hg version' which gives the version number.

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$hg version

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Now, what exactly is a repo? A repo/repository is a folder with contains all the files and information on all the changes that were made to it. To save disk space, hg doesn't save all files, but only saves only a series of changes made to the files.

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{{{Show the slide for 'We need a repo!'}}}

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Let's now see how to initialize a repo.

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cd working-directory/

$hg init

ls -a

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The .hg directory indicates that our book directory is now a hg repository. Mercurial keeps all the history of the changes made and a few other config files etc. in this directory.

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$hg status

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Gives the status of our repo. As a beginner, use it often.

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$hg help 'status'

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You can use 'hg help commandname' which gives the details about the command. For example.

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hg help status

{{{Show the slides for 'Status Codes'}}}

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Have a look at what various status codes, associated with the files mean. By looking at the codes, it is clear that our files are not being tracked by hg yet. Now let's move onto 'Adding Files'.

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$hg status

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This shows that none of the files in the folder have been added yet.

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$hg add

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This simply adds all the files in the (working) directory, to the repository. As expected, the status command shows an 'A' has been appended to the filenames. We could also specify files individually, for example

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$ hg add filename

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We have added a set of files to the repository, but we haven't told mercurial to remember these changes. Now let's take a snapshot of this working directory. This can be done by using commit command.

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$hg commit -u "username <user@domain.com>" -m "Commit message."

.. R20

The -u parameter allows to specify the user details. The parameter -m is used to attach a commit message which gives a description of the changes committed to the repository. Check the status of repository by typing

.. L20

$ hg st

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To see the history of changes made to our repository, we use hg log. We can view the change that we just made to our repository.

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{{{Show the slide 'Thumbnail views'}}}

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hg log gives the log of the changes made in the form of changesets. A changeset is a set of changes made to the repository between two consecutive commits. It also shows the date at which the commit was made.


.. R22

User information is set in the hgrc file. It can be either set globally or locally to the project.

For linux systems
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cat ~/.hgrc 
[ui]
username = username <user@domain.com>
editor = vim


.. R23


We have now set the user-name details for mercurial to use.

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{{{Show the slide 'Advice: commits, messages'}}} 

.. R24

1. Atomic changes; one change with one commit

#. Single line summary — 60 to 65 characters long

#. Followed by paragraphs of detailed description
 -  Why the change?
 - What does it effect?
 - Known bugs/issues?
 - etc.

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{{{Show the 'summary' slide'}}}

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This brings us to the end of the tutorial. In this tutorial, we have
learnt to,

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{{{Show self assessment questions slide}}}

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Here are some self assessment questions for you to solve

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{{{Show the solutions slide to self assessment questions }}}

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And the answers,


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{{{Show the thank you slide}}}

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Hope you have enjoyed this tutorial and found it useful.
Thank you