Leak when iterating through commits and diff them

When I run the code below on a production repository, i can see that the memory is all the time increasing and after about 3000 commits my pc crashes with out of memory.

For about 1000 commit it reserved about 500 MB Ram.

Code for Testsetup see here:
https://gist.github.com/Gentlehag/9f595ab13f459e22859fa5d9557e550b

PS: I also posted here:
http://stackoverflow.com/questions/39258639/possible-leak-when-reading-content

My target is to just iterate through all commits and getting all files that were changed in eahc commit.

Is there a better way ? Is this a bug?

首先运行 issue 的 GitHub Gist 中链接的复现，并在遍历提交和 diff 的过程中观察内存。将行为与 Stack Overflow 讨论进行比较，然后确定泄漏是在提交迭代中还是在 diff 处理过程中；完成的标准是复现增长现象，并确定经过验证的修复方案或有文档记录的替代方案。