If you want to host plugins or themes in the official WordPress repo, you’ll need a SVN client to checkout files and commit changes.
I also use Xcode for Mac on another machine which includes a SVN client however it takes up over 1 gb of space.
A SVN client is like a FTP client for transferring files to and from your local computer to the sub version repository where your code for plugins and themes is hosted.
All you need is the path to your folder
https://plugins.svn.wordpress.org/your-plugin-name as well as your WordPress username and password to checkout the entire plugin or theme folder to your local computer. Then you can manage versions locally ( version control ) on your working copy and commit changes to your remote ( WordPress ) repository.
Smart SVN Demo
The demo shows a small change to the readme.txt file in the local working copy of the trunk folder for a plugin named fonts.
Once you make any changes to your local working copy, you simply open smartsvn and commit the changes to your remote repo as seen in the above demo image.