How do I send a patch of committed revisions.

Hello,
 
While reading the documentation, I didn't find the answer to my problem.
I'm advocating the use of Subversion + TortoiseSVN at my client, with
success, but the people come to me with specific questions that I need
to answer.
 
One of these questions is that sometimes a user wants to help a
co-worker in the field with the latest updates and therefor send a patch
from the latest revisions. The co-worker in the field would be able to
identify the last updates he already has and request a patch for certain
revisions.
 
I've already found a way to create a patch of changes that have not been
committed yet, and I also found that it's easy to create a unified diff
by using the Merge tool, but this one eludes me. If I can succesfully
create a unified diff from selected revisions, how does this co-worker
apply them? I see the unified diff has filename comments describing the
repository and revision number the files are coming from. Does the Merge
tool ignore these comments? My initial test doesn't work.
 
If you would be so kind as to place my email in CC, as I don't always
have the time to browse through these archives.
 
Kind regards,
 
Dave

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