How to forbid a user to merge revision from other users

We have a subversion开发者_如何学运维 repository

• trunk
• q&a branch
• release branch

When Q&A are testing our web site we work on the Q&A branch, commit / update to resolve some bugs.

When we finish debugging we want to put all our fixes in the trunk, so we get the trunk , merge (without filtering on the revision n°) and then commit back to the trunk. The problem is : the web designer (who handle xslt and css files) can merge changes on code files (like c#) and when there is conflict he doesn't know what to do (it's the same for me when I have to resolve conflict about xslt files).

The only solution here is to merge only our revision, but it's prone to error (because there is a manual manipulation).

So I'd like to know if there is a way to tell to the server or to configure the client to merge only revision made by yourself, and have a super-user who can merge everything.