4.4. Getting Started: checkout

(Adapted from Version Control with Subversion under Creative Commons Attribution License v2.0.)

Most of the time, you will start using a Subversion repository by performing acheckoutof your project. Checking out a directory from a repository creates a working copy of that directory on your local machine. Unless otherwise specified, this copy contains the youngest (that is, most recently created or modified) versions of the directory and its children found in the Subversion repository:

$ svn checkout http://svn.example.com/svn/repo/trunk
      A    trunk/README
      A    trunk/INSTALL
      A    trunk/src/main.c
      A    trunk/src/header.h
      ...
      Checked out revision 8810.
      $

Although the preceding example checks out the trunk directory, you can just as easily check out a deeper subdirectory of a repository by specifying that subdirectory's URL as the checkout URL:

$ svn checkout http://svn.example.com/svn/repo/trunk/src
A    src/main.c
A    src/header.h
A    src/lib/helpers.c
...
Checked out revision 8810.
$

Since Subversion uses a copy-modify-merge model instead of lock-modify-unlock (see the section called “Versioning Models”), you can immediately make changes to the files and directories in your working copy. Your working copy is just like any other collection of files and directories on your system. You can edit the files inside it, rename it, even delete the entire working copy and forget about it.

While your working copy is “just like any other collection of files and directories on your system,” and you can edit files at will, you must tell Subversion about everything else that you do. For example, if you want to copy or move an item in a working copy, you should use svn copy or svn move instead of the copy and move commands provided by your operating system. We'll talk more about them later in this chapter.

Unless you're ready to commit the addition of a new file or directory or changes to existing ones, there's no need to further notify the Subversion server that you've done anything.

What Is This .svn Directory?

The topmost directory of a working copy—and prior to version 1.7, every versioned subdirectory thereof—contains a special administrative subdirectory named .svn . Usually, your operating system's directory listing commands won't show this subdirectory, but it is nevertheless an important directory. Whatever you do, don't delete or change anything in the administrative area! Subversion uses that directory and its contents to manage your working copy.

Notice that in the previous pair of examples, Subversion chose to create a working copy in a directory named for the final component of the checkout URL. This occurs only as a convenience to the user when the checkout URL is the only bit of information provided to the svn checkout command. Subversion's command-line client gives you additional flexibility, though, allowing you to optionally specify the local directory name that Subversion should use for the working copy it creates. For example:

$ svn checkout http://svn.example.com/svn/repo/trunk my-working-copy
A    my-working-copy/README
A    my-working-copy/INSTALL
A    my-working-copy/src/main.c
A    my-working-copy/src/header.h
...
Checked out revision 8810.
$

If the local directory you specify doesn't yet exist, that's okay, svn checkout will create it for you.

4.4.1. Exercise - Initial Checkout of the Sample Codebase

Create a local checkout of the sample CS390X repository.