I just tried out RapidSVN to update a Gnome-RDP branch, and it worked pretty well. I just installed it from Synaptic.
Here is the URL that I used to get just the branch:
I just used the checkout option from the Repository Menu to get the copy of the branch.
Then, I used Meld to copy my changes from my working directory into this branch. Then, I used the Commit option in the Modify Directory.
Then, I found my commit online, and it looked like it did what I needed it to do.