Very annoying because I like both tools.
So I went searching and found this document (online) in the help files. So I tried to put that DLL in the Tortoise bin directory, but of course that wouldn't work because they've renamed everything with a leading "T."
So I downloaded the actual SVN client from Subversion. Then put the dll in that directory...now I open up SQLDev and get this seay32.dll (or something like that) missing. Awesome.
Back to searching and I found this one. user594768 has only 2 posts but this one did the trick.
First, download the 1.2.0 SVNKit from here.
Then, do the following:
- svnkit-javahl.jar (rename into svnjavahl.jar)
Start SQL Developer and go to Tools --> Preferences --> Versioning and it should read:
SVN/1.5.2 SVNKit/1.2.0 (http://svnkit.com/) r4949
This works for both JDeveloper and SQL Developer.