Issue submitted to upstream with my guess and explanation.

https://github.com/magit/libegit2/issues/121

This issue is not trivial and there's no way to workaround it IMO. 
-- 
Retrieve my PGP public key:

  gpg --recv-keys D47A9C8B2AE3905B563D9135BE42B352A9F6821F

Zihao