[PATCH] Update rename/copy similarity estimator.

[PATCH] Update rename/copy similarity estimator.

The second round similarity estimator simply used the size of
the xdelta itself to estimate the extent of damage.  This patch
keeps that logic to detect big insertions to terminate the check
early, but otherwise looks at the generated delta in order to
estimate the extent of edit more accurately.

Signed-off-by: Junio C Hamano <junkio@cox.net>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>