How to diff one file to an arbitrary version in Git?

Question

How can I diff a file, say pom.xml, from the master branch to an arbitrary older version in Git?

Answer 1

If you are fine using a graphical tool (or even prefer it) you can:

gitk pom.xml

In gitk you can then click any commit (to "select" it) and right click any other commit to select "Diff this -> selected" or "Diff selected -> this" in the popup menu, depending on what order you prefer.