It seems that all of the initial Google results for \"using subversion with xcode\" are actually just tutorials for installing and configuring svn and Xcode, as opposed to a
I came across these - no idea how well they work, but wanted to add some resources if I could:
if you want to work with svn through a gui interface then i suggest you use eclipse + subclipse plugin (which have more features and much more reliable and easy than svn on xcode)..
you will work in xcode as normal but you will use eclipse only as an svn client (by creating a general project in eclipse and make it points to your xcode project directory )
and here is a tutorial of how to install subclipse
With XCode4 you can perform almost all of your SCM tasks from within the IDE itself, this is a great step forward.
Here is a link to the official guide : http://developer.apple.com/library/mac/#documentation/ToolsLanguages/Conceptual/Xcode4UserGuide/SCM/SCM.html#//apple_ref/doc/uid/TP40010215-CH7-SW26
Unfortunately you still have to use the Terminal command line to add a new project to SCM, this is also clearly documented in the link above.
What it does not tell you is that you also need to manually add ignore instructions to your SCM configuration otherwise you are going to end up with user settings and build outputs in your repositories. I am currently figuring out the list and I will update this answer once I have it finalised.
PS : I know this question is quite old now but I have added this for those of you who arrive here looking for answers like I did.
PPS : Terminal command line increases probability of human error, takes longer, is more complex and is less transparent to end users. Overall the omission of being able to add projects to SCM from within XCode is poor design, I expected better from Apple who are usually good at simplifying UI. For the command line fans out there you might feel L337 but try managing a team of programmers and being responsible for their code, command line is not your friend.
As has been mentioned in many other answers, the svn client with Xcode is quite weak (and that is being kind).
Personally, I think that running Eclipse just to get access to a svn client is a bit heavy handed.
I would suggest two answers: