Querying an XML document using XMLStarlet

I use Maven to manage my Java build process. Maven, like Ant, uses XML to store information about your project and how to build it.

Yesterday, a thought occurred to me – What if I wanted to write a script that would do post-packaging of the Maven-built artifact(s)?

For example, what if I wanted to take the Maven-built artifact and distribute it via an OS X disk image? Or even something as simple as packaging the source into a tar.gz?

A simple shell script would be easy enough to cook up – but without repeating myself, how could I do it such that the subsequent packages are named according to the same version declared in the Maven pom.xml file?

This got me to thinking about how to query XML, possibly using XPath from a shell script or the command line. I thought I might have to roll out my own XML-XPath command line processor, but fortunately somebody else beat me to it (thanks, God for all the wonderful people on teh internets) with XMLStarlet.