Congratulations on creating a new project on Wowace or Curseforge! Now you want to check out your shiny, barren, repository to create your working copy folder on your hard drive, and ... wait, error! Link not found! But it is right there, under your project's Source URL!!
Fear not, the fix is easy, if a bit tedious. The old WA/CF system automatically created the trunk, tags, and branches folders for you, but the new system, regardless of what you see in the Source URL does not.
While this guide talks about TortoiseSVN, the steps should be almost the same for other repository systems, albeit you might have some renamed tools within their respective clients.
NOTE: existing projects that were converted to the new system have tags, branches, and trunk folders intact, so there is nothing for you to do other than more hacking!
New projects how-to:
Navigate to Interface\AddOns, but not inside the \AddOns\ folder. You do not want to see the list of installed AddOns, but the parent folder that contains your AddOns.
Right click and pull up TortoiseSVN's repo browser from the submenu.
"Navigate to Interface\AddOns, but not inside the \AddOns\ folder."
Any clue for those of us new to this system (but not new to coding) HOW or WHERE to do this navigation? I've been searching this site for a week and I have yet to find the first hint of how to get there. I can't tell if the lack of non-jargon-based "help" is intentional tech-snobbery or just the cluelessness that sometimes comes with people overly focused on a single aspect of technology.
Use either Windows Explorer or the Mac Finder to go your World of Warcraft folder. Inside that, you will see Interface, along with Cache, WTF, Logs, and other stuff. Inside Interface is the AddOns folder.
I would tell you where your World of Warcraft folder is, but that could be very different user to user. On Windows, the generic path is C:\Program Files(x86)\World of Warcraft, but some people have installed the game elsewhere.
On the Mac, I know you can right-click the WoW icon to start browsing into the folder structure of the game, but I do not remember the exact steps because I currently do not own a Mac.
The other method to find your AddOns folder is via the Curse App (same trick as the v5 Curse Client); RIGHT click any AddOn in your installed list and select "Browse Folders..." which will open that AddOn's folder. Then just go up one level in your folder tree.
For example, if I right-clicked AdiBags, Explorer or Finder would open right to World of Warcraft\Interface\AddOns\AdiBags, and then I'd go up one level to see all my installed AddOns. You know you have found the correct folder when you see about two dozen folders starting with the name "Blizzard_".
Thanks for the updated info Myrroddin, ran across one from 2006(?) that was a bit out of date. There are however a few missing steps that some may not be aware of (ie: noobs like me).
This is for Windows based machines. I have tested on Windows 7 and 10, working on both.
You will need TortoiseSVN, an open source and free program (even for commercial use). You can download it here. You will need to reboot after install, as it integrates with Windows Explorer.
After the reboot browse over to your WoWAce project page, and click on Settings. On the menu on the left select Source. Select CurseForge->Subversion as your repository. Under Automatic packaging, select Package tagged commits. Save your changes. You will now have a Source menu item in the horizontal menu under your addon name. This is the source location mentioned in Myrroddin's instructions.
When you create the initial "trunk" folder, as mentioned in the first post, it will ask for a username and password. Be sure to have them ready. You can save the credentials when creating the folder, or untick the box and it will just remember them for the current session.