Version Control Tutorial

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VERSION CONTROL

• What is Version Control why is it needed?
• Version control software is an essential part of
  the modern software teams professional
  practices. It provides you with many
  capabilities, such as
• Maintain multiple versions of code.
• An ability to go rollback to previous version.
• Developers can work in parallel.
• Audit traceability with clear picture on whom,
  when, where and what are the changes.
• Synchronize the code.
• Copy/Merge/Undo the changes.
• Find out the difference between versions.
• Provides full backup without occupying much
  space.
• Review the history of the changes.
• Capable for both small and large scale projects.
• Ability to share and use the code amongst
  remotely located developers.
• Version control systems are a category of
  software tools that help a software team manage
  changes to artifacts over a period of time. With
  version control, multiple versions of the same
  file can be easily maintained and any specific
  version can be recalled instantly.
• Software developers working in teams are
  regularly creating new and updating the existing
  source code. The code for a project, application
  or any software component is typically structured
  in a folder structure
• or a file tree. Suppose, a developer on a
  particular team is working on a new feature while
  another developer fixes an unrelated bug by
  changing the code, each developer can update
  several parts of the file tree. There will surely
  be consistency issues.
• Version control helps teams resolve these kinds
  of problems, by keeping a track of every single
  change made by each contributor and helps prevent
  conflict issues. We all probably have, at some
  point, figured out different ways to manage
  multiple versions of a file by adding suffixes or
  numbers and then deal with a new final version,
  in the end. For example commenting out certain
  code blocks to temporarily disable a
  functionality, without deleting it, fearing it
  could be of use later. Version control is the
  panacea in such situations.
• Types of Version Control
• There are two types of VCS

repository.
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• It may seem pretty convenient to maintain a
  single repository, but there are some major
  drawbacks in the approach, like
• It is not locally available, so you always have
  to be connected to a network to perform any
  action.
• Given everything is centralized, if the central
  server gets crashed or corrupted, the entire data
  of the project will be lost.
• Distributed VCS is the saviour in such scenarios.
  Let us understand what is Distributed VCS.
• Distributed VCS
• Distributed Version Control systems do not depend
  on a central server to store all the versions of a

project file.
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In Distributed version control system, each
contributor has his own local copy or clone of
the remote repository, so everyone maintains
their own local repository which contains all the
files and metadata present just like the main
repository.As you can see in the above diagram,
every programmer maintains their own local
repository, which is actually a copy of the
central repository on their local machine. They
can commit and update their copy without any
intrusion. They can update their local repository
with fresh data from the central server by an
operation called pull and can commit changes
from their repository to the main repository by
an operation called push.

• Distributed VCS gives you the following
  advantages
• All local operations (except push pull) are
  very quick because the tool only needs to access
  the local

system, not a remote server. Hence, you are not
always dependent on an internet connection.
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• Committing a new set of changes can be done
  locally without manipulating the data on the
  main repository. Once you have a group of changes
  ready, you can push them all at once.
• Since every developer has a replica of the
  project repository, they can share changes with
  each other and do a peer review before updating
  the main repository, with the code commits.
• If the central server gets crashed at any point
  of time, the lost data can be easily recovered
  from any one of the contributors local
  repositories.

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Version Control Tools
Version control tools enable collaboration,
maintain versions, and track changes across the
team. These tools help you deal with an unlimited
number of people, working on the same code base,
without ensuring that files are delivered back
and forth. Below are some of the most widely-used
and most popular open-source version control
systems and tools available in the market 1.
CVS Features
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• Client-server repository model.
• Multiple developers might work on the same
  project in parallel.
• CVS client will have a working copy of the file
  up-to-date and requires manual intervention only
  when an edit conflict occurs.
• Keeps a historical snapshot of the project.
• Anonymous read access.
• There is an Update command which updates the
  local copies to the latest version.
• Can uphold different branches of a project.
• Excludes symbolic links to avoid a security risk.
• Uses delta compression technique for efficient
  storage.
• Pros
• Excellent cross-platform support.
• Robust and fully-featured command-line client
  permits powerful scripting
• Helpful support from vast CVS community
• Good web browsing of the source code repository
  is allowed.
• Its quite an old, well known established tool.
• Good option in the collaborative open-source
  world.
• Cons
• No integrity checking for source code repository.
• Does not support atomic checkouts and commits.

• Client-server repository model.
• Directories are versioned.
• Each operation is versioned.
• Supports atomic commits.

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Versioned symbolic links.
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• Free-form versioned metadata.
• Space efficient binary diff storage.
• Branching is not dependent upon the file size and
  this is a cheap operation.
• Other features merge tracking, full MIME
  support, path-based authorization, file locking,
  standalone server operation.
• Pros
• Good supporting GUI tools like TortoiseSVN,
  available
• Supports empty directories.
• Have better windows support as compared to Git.
• Easy to set up and administer.
• Known to integrate well with Windows, leading IDE
  and Agile tools.
• Cons
• Does not store the modification time of files.
• Does not deal well with filename normalization.
• Does not support signed revisions.
• 3. Git
• Features

• Provides strong support for non-linear
  development.
• Distributed repository model.
• Compatible with protocols like HTTP, FTP, ssh.
• Capable of managing different-sized projects
  efficiently
• Cryptographic authentication of history.
• Pluggable merge strategies.
• Toolkit-based design.
• Periodic explicit object packing.
• Garbage accumulates until collected.
• Pros
• Super-fast and efficient performance.
• Cross-platform
• Code changes can be tracked very easily and
  clearly.
• Easily maintainable and robust.
• Offers an incredible command line utility tool
  named git bash.
• Also offers GIT GUI where you can very quickly
  re-scan, state change, sign off, commit push
  the code quickly with just a few clicks.
• Cons
• Complex and bigger history log becomes difficult
  to understand.

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Does not support keyword expansion and timestamp
preservation.
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4. Mercurial Mercurial is a distributed
revision-control tool written in python. The
supported operating systems are Unix-like,
Windows and macOS. Features

• High performance and scalability.
• Advanced branching and merging capabilities.
• Fully distributed collaborative development.
• Decentralized
• Handles both plain text and binary files
  robustly.
• Possesses an integrated web interface.
• Pros
• Fast and powerful
• Easy to learn
• Lightweight and portable.
• Conceptually simple
• Cons
• All the add-ons must be written in Python.
• Partial checkouts are not allowed.
• Quite problematic when used with additional
  extensions.
• 5. Bazaar
• Bazaar is a DVCS, which provides a great,
  friendly user experience. Bazaar has a unique
  feature that it can be deployed either with a
  central code base or as
• a distributed code base.
• Features

• It has commands similar to SVN or CVS.
• It allows you to be working with or without a
  central server.
• Provides free hosting services through the
  websites Launchpad and Sourceforge.
• Supports file names from the entire Unicode set.
• Pros
• Directories tracking is supported very well in
  Bazaar (not there in tools like Git, Mercurial)

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Its plugin system is fairly easy to use.
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• High storage efficiency and speed.
• Cons
• Does not support partial checkout/clone.
• Does not provide timestamp preservation.

CVCS (SVN)
DVCS (Git)
You dont checkout code from a central
repository
There is a central server repository which holds
the "official copy" of the code
The server maintains the version history of the
repository
You clone the entire repository and pull changes
from it, on your local copy
You make "checkouts" on your local machine You
make modifications on the checked out code
Your local repo is a replica of everything on the
remote server
yours is just as good as theirs
Your changes are not versioned
When you have completed, you check in your code
changes back to the server
Many operations are local
check in/out from local repo commit changes to
local repo Local repo keeps version history When
you are ready to commit your changes, you can
push them back to server
Your check-in increments the repositorys version
Git maintains snapshots of the entire state
Centralized VCS like SVN tracks versions
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on every file.
of the project.
Each committed version of the overall code has a
copy of each file in it. Not every file changes
with each commit, so more redundancy, but faster
Git is way more popular in comparison to other
version control tools available in the market.
It is time we take a deep dive into Git. For more
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