Who doesn’t know the following situation:
The file somestuff.c is in the HEAD revision, but it is not working anymore. Now you want to revert it to the revision 10 (which is may be HEAD-1). One way doing that is to update to the files correct version by:
svn up -r 9 somestuff.c
Then copy the file to a file temp.c, update the folder to HEAD by svn up, then move back the temp.c file to somestuff.c. Simple, isn’t it?
Actually there is a lot easyier way:
svn merge -r HEAD:9 somestuff.c