identifying all files modified since the last tag

[Ender]

I'm hoping someone can provide me with a somewhat simple way of
determining which files in a project have been modified since the last
tag was applied.

currently, to accomplish this, I'm checking out the module using the
tag to a temporary directory, then performing an update without the
tag, then grepping through the output to determine which files were
updated, and using that as my list of modified files. This to me seems
very clunky, and it seems to me that there should be an easier way.
thanks in advance

Ender