git-reference/index.html

---
layout: reference
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<div class="box">
  <h2>Introduction to the Git Reference</h2>
  <div class="block">
    <p>
    This is the Git reference site. This is meant to be a quick
    reference for learning and remembering the most important and
    commonly used Git commands.  The commands are organized into
    sections of the type of operation you may be trying to do, and
    will present the common options and commands needed to accomplish
    these common tasks.
    </p>
    <p>
    Each section will link to the next section, so it can be used
    as a tutorial.  Every page will also link to more in-depth
    Git documentation such as the offical manual pages and relevant
    sections in the <a href="http://progit.org">Pro Git book</a>, 
    so you can learn more about any of 
    the commands. First, we'll start with thinking about source code 
    management like Git does.
    </p>
  </div>
</div>

<div class="box">
  <h2>How to Think Like Git</h2>
  <div class="block">
    <p>
    This first thing that is important to understand about Git is
    that it thinks about version control very differently than 
    Subversion or Perforce or whatever SCM you may be used to. It
    is often easier to learn Git by trying to forget your assumptions
    about how version control works and try to think about it in the
    Git way.
    </p>

    <p>
    Let's start from scratch.  Assume you are designing a new source 
    code management system.  How do you do basic version control before
    you used a tool for it?  Chances are that you simply copied your 
    project directory to save what it looked like at that point.
    </p>

    <pre> $ cp -R project project.bak </pre>

    <p>
    That way, you can easily revert files that get messed up later, or 
    see what you have changed by comparing what the project looks like
    now to what it looked like when you copied it.
    </p>

    <p>
    If you are really paranoid, you may do this often, maybe putting the
    date in the name of the backup:
    </p>

    <pre> $ cp -R project project.2010-06-01.bak </pre>

    <p>
    In that case, you may have a bunch of snapshots of your project that 
    you can compare and inspect from. You can even use this model to 
    fairly effectively share changes with someone.  If you zip up your
    project at a known state and put it on your website, other developers
    can download that, change it and send you a patch pretty easily.
    </p>

    <pre>
 $ wget http://sample.com/project.2010-06-01.zip
 $ unzip project.2010-06-01.zip
 $ cp -R project.2010-06-01 project-my-copy
 $ unzip project.2010-06-01.zip
 $ cd project-my-copy
 $ (change something)
 $ diff project-my-copy project.2010-06-01 > change.patch
 $ (email change.patch)</pre>

    <p>
    Now the original developer can apply that patch to their copy of the
    project and they have your changes. This is how many open source 
    projects have been collaborated on for several years.
    </p>

    <p>
    This actually works fairly well, so let's say we want to write a tool
    to make this basic process faster and easier.  Instead of writing a tool
    that versions each file individually, like Subversion, we would probably
    write one that makes it easier to store snapshots of our project without
    having to copy the whole directory each time.
    </p>

    <p>
    This is essentially what Git is. You tell Git you want to save a snapshot
    of your project with the <code>git commit</code> command and it basically 
    records a manifest of what all of the files in your project look like at 
    that point.  Then most of the commands work with those manifests to see
    how they differ or pull content out of them, etc.  
    </p>

    <center><img src="./images/snapshots.png"/></center>

    <p>
    If you think about Git
    as a tool for storing and comparing and merging snapshots of your project,
    it may be easier to understand what is going on and how to do things 
    properly.
    </p>

  </div>
</div>

<p><a href="/creating">On to Getting and Creating Projects &#187;</a></p>