Git call graph

Hi,

I just did this for fun, if you are busy, you can stop reading now,
this mail is not about anything important. :-)

I thought it would worth a try to make a graph about git calls, when a
script calls an other git program. I tracked two types of calls:

- when a bultin calls an other builtin (like git reset calls
  git read-tree)

- when a script calls a builtin (like git merge-resolve calls
  git write-tree)

Here is the result:

http://vmiklos.hu/pic/git-call-graph.png

The code that was used to generate the graph is available at the 'graph'
branch of git://repo.or.cz/git/vmiklos.git.

If you check out that branch, you can simply type 'make' to generate the
picture, or you can read some minimal documentation (README).

And now I should stop playing with it, in fact it took much more time
than I expected. ;-)