You can use git blame -l filename to get the SHA1 hash from when the line was changed.
You also can use –reverse:
–reverse
Walk history forward instead of backward. Instead of showing the revision in which a line appeared, this shows the last revision in which a line has existed. This requires a range of revision like START..END where the path to blame exists in START.
See: http://www.kernel.org/pub/software/scm/git/docs/git-blame.html