up libgit2
repo
try to merge v0.20.0
still merge conflict
add -lrt
use git_patch_from_diff instead git_diff_get_patch, but segment fault
Fix get delta.
Merge pull request #2 from xutao/pygit2:pr/18

Fix get delta.
还有一个 test_refspec
test refspec
Merge pull request #18 from huanghuang/pygit2:new

updated with upstream pygit2
Fix no patch diff.
Merge pull request #19 from xutao/pygit2:patch

Fix no patch diff.
Remove rt.
Fix rt.
Merge pull request #20 from xutao/pygit2:setup

Remove rt.
Merge branch 'master' into gh_douban

Conflicts:
	.gitmodules