Added examples how to change the directory

It's very useful to have example for each OS how to change the directory
in Git (especially for Windows because the syntax is different from the
default syntax — C:/Users/your_repository).
Second try to contribute to this project.

Author: haripetrov

book/02-git-basics/sections/getting-a-repository.asc

@@ -7,7 +7,25 @@ The second clones an existing Git repository from another server.
 
 ==== Initializing a Repository in an Existing Directory
 
-If you're starting to track an existing project in Git, you need to go to the project's directory and type:
+If you're starting to track an existing project in Git, you need to go to the project's directory. If you've never done this, it looks a little different depending on which system you're running:
+
+for Linux:
+[source,console]
+----
+$ cd /home/user/your_repository
+----
+for Mac:
+[source,console]
+----
+$ cd /Users/user/your_repository
+----
+for Windows:
+[source,console]
+----
+$ cd /c/user/your_repository
+----
+
+and type:
 
 [source,console]
 ----