git failed to build when binnmu'd for the time64 transition and also in lucas's test build a few days earlier. This was filed as bug 1066794.
Andrey Rakhmatullin responded to the bug report saying he was unable to reproduce the failure. Michael Hudson replied with a post suggesting that the failure may be related to libcgi-pm-perl, though he did not make it clear which version of libcgi-pm-perl he was testing with. Andrey noted that the version of libcgi-pm-perl in his local tests was newer than the version used in the failed builds. Ubuntu temporally disabled tests in git, but have since re-enabled them, and the package built successfully on all Ubuntu architectures. I would suggest therefore that it makes sense to retry the binnmus as there is a good chance that whatever caused the issue has since been fixed.