[PATCH] diff-tree: --find-copies-harder

[PATCH] diff-tree: --find-copies-harder

Normally, diff-tree does not feed unchanged filepair to diffcore
for performance reasons, so copies are detected only when the
source file of the copy happens to be modified in the same
changeset.  This adds --find-copies-harder flag to tell
diff-tree to sacrifice the performance in order to find copies
the same way as other commands in diff-* family.

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