[PATCH] Add git-var a tool for reading interesting git variables.

Sharing code between shell scripts and C is a challenge.  The program
git-var allows us to have a set of named values that a shell script can
interrogate and a normal C program can simply call the functions that
compute them.  Allowing sharing when computing plain test values.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>