This is the first time I've reported a bug with Git so please forgive
me if this isn't the right place, format, etc.
If git blame --porcelain (or --line-porcelain or --incremental) is run
on a file that has uncommitted changes any uncommitted lines have the
wrong previous sha. Instead of the sha the last time that line was
changed or even the last time the file was changed it seem to return
the last commit in the repository. This seems to only affect
uncommitted lines, other line seem to be populated properly.
I am using git version 2.10.0 on macOS 10.12 (16A323).
Please let me know if I can provide any more information.