Make svn diff produce output for new files added on another branch

After merging changes from a branch different from the working one
I could get files added on that other branch, and the svn stat
would look like:

 M .
A + a_new_file

Issuing svn diff at this point doesn't include the "a_new_file"
content in the output. Could svn diff be instructed to include the
"a_new_file" content in the output?

Similarly, when working on a feature branch and periodically
syncing with trunk (for example) I often like to compare what I've
got changed on the branch (whether the merge hasn't gone bad, e.g.
after resolving conflicts) before committing the just merged
changes, like:

svn diff --old=^/trunk --new=.

And I get a problem that files which were added on trunk (and just
merged but not committed) appear as deleted in the produced
output. Does this appear as bug?

-- 
Stanimir