Change libgit2 to github.
Merge remote-tracking branch 'code/master' into douban
Merge branch 'master' into gh_douban

Conflicts:
	.gitmodules
Merge remote-tracking branch 'upstream/master' into gh_douban
Merge remote-tracking branch 'upstream/master' into gh_douban
Merge remote-tracking branch 'origin/master' into gh_douban
Merge remote-tracking branch 'origin/master' into gh_douban

Conflicts:
	.gitmodules
Bump libgit2.
Merge remote-tracking branch 'upstream/master' into gh_douban
Merge remote-tracking branch 'upstream/master' into gh_douban
Merge remote-tracking branch 'douban/douban' into bump2