Reallocated wrong size.
Noticed on Ubuntu 7.04 probably because it has some malloc diagnostics in libc:
"git-read-tree --reset -u HEAD" aborted in the test. Valgrind sped up the
debugging greatly: took me 10 minutes.
Signed-off-by: Alex Riesen <raa.lkml@gmail.com> Signed-off-by: Junio C Hamano <junkio@cox.net>