git pickaxe -- problems with relative filenames

We seem to have a difference in the handling of relative filenames
within a repository between git blame and git pickaxe.  Specifically git
pickaxe seems to always require names as if it were run in the top of
the project:

apw@pinky$ pwd
/home/apw/git/git/Documentation
apw@pinky$ git blame git.txt | head -2
7984eabe (Sebastian Kuzminsky 2005-05-19 10:24:54 -0600   1) git(7)
2cf565c5 (David Greaves       2005-05-10 22:32:30 +0100   2) ======
apw@pinky$ git pickaxe git.txt | head -2
fatal: cannot stat path git.txt: No such file or directory
apw@pinky$ git pickaxe Documentation/git.txt | head -2
7984eabe (Sebastian Kuzminsky 2005-05-19 10:24:54 -0600   1) git(7)
2cf565c5 (David Greaves       2005-05-10 22:32:30 +0100   2) ======

This seems inconsistent? Is this expected behaviour?