git diff is slow (--patience is fast)

Warning, downloaded files are 7.5Mb each.

~ $ git --version
git version 1.7.6
~ $ mkdir tmp
~ $ cd tmp
~/tmp $ git init
Initialized empty Git repository in /home/marat/tmp/.git/
~/tmp $ wget http://slonopotamus.org/git-diff/foo 2> /dev/null 
~/tmp $ git add -A
~/tmp $ git commit -am "initial"
[master (root-commit) 6b68e83] initial
 1 files changed, 410461 insertions(+), 0 deletions(-)
 create mode 100644 foo
~/tmp $ wget http://slonopotamus.org/git-diff/foo2 -O foo 2> /dev/null 
~/tmp $ time git diff > /dev/null 

real 0m6.513s user 0m6.490s sys 0m0.020s ~/tmp $ time git diff --patience > /dev/null

real 0m0.237s user 0m0.180s sys 0m0.050s

Could something be done to `git diff` speed? I would be happy with patience diff, but other git commands call standard diff algorithm internally without giving an option to choose patience.

gprof output against git master: http://slonopotamus.org/git-diff/gmon.txt