OK, you want to update the current repository with one of your previous revisions. It could be a single file you want to update
Here is what you would do:
Lets assume you have a module/folder svnrepos and it has two files soap.php and xml.php
And lets say you want to update and commit the file soap.php with the previous revision number
1. Go to the folder svnrepos
2. type svn up to make it up-to-date
3. type svn log –limit 10 (or whatever deep you want to go the past revisions
4. From there you would grab the revision number you want to get back to.
Now the trick is merging the current revision and the one you want to get back to: lets say the revision number you want to get back is 7865
5. do svn merge full/path/to/repository/svnrepos/soap.php@HEAD full/path/to/repository/svn/repos/soap.php@7865 soap.php
This would update your local, which was up-to-date, to the one from 7865.
6 svn st would show you soap.php is updated
7. svn commit -m ‘Reverting back to old revision’
ZAT is IT!!