builtin difftool parsing issue

Sadly, I haven't been able to figure out how to get the mbox file from
this tread into gmail, but wanted to report a parsing issue I've found
with the builtin difftool.

Original Patch:
https://public-inbox.org/git/ac91e4818cfb5c5af6b5874662dbeb61cde1f69d.1480019834.git.johannes.schindelin@gmx.de/#t

+ *status = *++p;
+ if (!status || p[1])
+ return error("unexpected trailer: '%s'", p);
+ return 0;

The p[1] null check assumes the status is only one character long, but
git-diff's raw output format shows that a numeric value can follow in
the copy-edit and rename-edit cases.

I'm looking forward to seeing the builtin difftool land.  I came across it
while investigating adding --submodule=diff (expanding on diff's
recent addition) support and this looks more promising then the perl
script.  Hopefully I will make some progress.  Any tips/pointers would
be greatly appreciated.

Thanks