blame --line-porcelain is providing me with funny output

Hi, everybody!

As part of my improvements to difflame I want to use revision information as provided by blame --line-porcelain so that I can avoid some git calls to cat-file -p to get revision information hoping that information would be a match. However I'm not finding that to be the case.

$ git blame --no-progress -w --line-porcelain -L 72,72 4e59582ff70d299f5a88449891e78d15b4b3fabe -- t/lib-submodule-update.sh

3290fe6dd2a7e2bb35ac760443335dec58802ff1 72 72 1
author Stefan Beller
author-mail <somemail@gmail.com>
author-time 1484160452
author-tz -0800
committer Junio C Hamano
committer-mail <somemail@pobox.com>
committer-time 1484337771
committer-tz -0800
summary lib-submodule-update.sh: reduce use of subshell by using "git -C"
previous d7dffce1cebde29a0c4b309a79e4345450bf352a t/lib-submodule-update.sh
filename t/lib-submodule-update.sh
                       git -C sub1 checkout modifications &&

If we then take a look at the information on that revision using cat-file -p on the revision:

$ git cat-file -p 3290fe6dd2a7e2bb35ac760443335dec58802ff1

tree 7df89dad28ec8b08875395265a3f2e13ba180174 parent d7dffce1cebde29a0c4b309a79e4345450bf352a author Stefan Beller <somemail@google.com> 1484160452 -0800 committer Junio C Hamano <somemail@pobox.com> 1484337771 -0800

(which, just in case, resembles the information provided by git show... but is simpler to parse with cat-file).

Committer mails are matching, however author mail does not match between line-porcelain and cat-file. Is there a reason for that?

Thanks in advance.