plumbing: object, rename calculation uses too much memory
plumbing: object, rename calculation uses too much memory

The size of the similarity matrix is not limited and can be quite big
when lots of files are deleted and added in a commit.

Signed-off-by: Javi Fontan <bd6f2f0212e303b54f36d84bb19ae60fa8e400a6@gmail.com>

go-git/go-git,go-git/go-git