Error -> Build failed -> Please upgrade your Subversion client to use this working copy
Xcode doesn't yet support SVN 1.7. Only 1.6 is supported. In order to fix your problem, you'll need to switch to using an SVN 1.6 compatible working copy.
Since SVN 1.7 client is unable to work with 1.6 working copies at all, you'll need to remove SVN 1.7.x from your client and revert to 1.6. (Or perhaps just adjust your PATH so the SVN 1.6 tools are first.) Once 1.6 is back, delete or move aside your existing working copy and check out a fresh copy with SVN 1.6. Now Xcode should be able to work with your working copy.
Note that you can freely use SVN 1.6 client with an SVN 1.7 server. Some of the newer features won't be available, but it will work. There's no need to downgrade the server or your server-side repositories.
Keep an eye on the Xcode release notes in updates as I'm sure Apple will note when Xcode is capable of using SVN 1.7. When a 1.7 compatible release of Xcode becomes available, it should then be safe to upgrade your client to 1.7 and migrate your working copy again.
There is a post that appears to imply that you can fool XCode into using svn 1.7 client by changing your PATH and setting up a couple of soft links in strategic places. Unfortunately, the post is in Chinese. Fortunately, Google translate and the presence of UNIX commands make it possible to decrypt what the post is saying. I will try it in the next few days, and update the answer if anything useful comes out of this exercise.
EDIT: I tried the steps from the post, and it worked. Here is what I did:
- Downloaded and installed svn client 1.7.2 into
/opt/subversion - Added /opt/subversion/bin to my
PATHin.bash_profile - Created a backup directory
/Developer/usr/bin/orig.svn - Moved
/Developer/usr/bin/svn*to/Developer/usr/bin/orig.svn - Ran
ln -s /opt/subversion/bin/svn* /Developer/usr/bin/
After that I re-started XCode, went to Organizer, and was able to attach a working copy of a checkout created with svn 1.7.2 client. Organizer showed a green dot next to the repository, displayed a list of revisions, etc., so at this point I believe that the trick has worked.