Figure it out.
There is this phrase in the help text regarding the path: "Relative to the workspace root." So the question becomes, what is "the workspace root?" Well, looking at the ~/.hudson/jobs directory, I noticed that for job Foo Bar, there was this directory structure:
~/.hudson/jobs/Foo Bar/workspace/foobar
That last foobar is the project directory from Subversion, and it is that foobar directory that contains my project (that it the Mavne or
Ant build script resides there and it is basedir for the builds. However, foobar is not "the workspace root." Instead, the workspace directory is the workspace root.
The other thing I had to figure out is that the syntax for the properties is not well documented. It should really say:
${FILE, path="xxx"} where xxx is the relative path to the file
Thus this worked for me:
${FILE, path="foobar/pom.xml"}
I received an email with the contents of the POM.