I did some reading into the relevant code in cgit: https://github.com/gitster/git/blob/master/date.c#L604.
If I read the code correctly, the C code interprets "--700" as a double-negative, or equivalent to +0700. I believe that implementation is a mistake, but if copying that mistake into dulwich is the proper fix, I will put together a patch.
I did some reading into the relevant code in cgit: https:/ /github. com/gitster/ git/blob/ master/ date.c# L604.
If I read the code correctly, the C code interprets "--700" as a double-negative, or equivalent to +0700. I believe that implementation is a mistake, but if copying that mistake into dulwich is the proper fix, I will put together a patch.