add note about using --global only if its on own machine

Author: brianamarie

book/05_local_git_configs.md

@@ -30,6 +30,7 @@ These are the repository level configurations. They only apply to the specific r
 
 > The default value for git config is `--local`.
 
+
 ### Viewing Your Configurations
 
 If you would like to see which config settings have been added automatically, you can type `git config --list`. This will automatically read from each of the three config files and list the setting they contain.
@@ -46,6 +47,8 @@ $ git config --global --list
 
 ### Configuring Your User Name and Email
 
+The directions below are using `--global`. This is fine if you are on your own machine. However, if you are using a shared computer, omit the `--global` flag so that the settings will only be stored to the repository. When you work in another repository on this same computer, you will need to set these configurations again.
+
 Git uses the config settings for your user name and email address to generate a unique fingerprint for each of the commits you create. You can't create commits without these settings:
 
 ```sh