Update libgit2
tree539d6c8e33b2f7468c41debb4aacf4f319a47a2e
-rw-r--r-- 600 .gitignore
-rw-r--r-- 975 .gitmodules
-rw-r--r-- 639 .mailmap
-rw-r--r-- 231 .tgitconfig
drwxr-xr-x - Languages
-rw-r--r-- 3974 README.md
-rw-r--r-- 3119 appveyor.yml
-rw-r--r-- 6137 architecture.txt
-rw-r--r-- 2998 build.txt
drwxr-xr-x - contrib
drwxr-xr-x - doc
drwxr-xr-x - ext
-rw-r--r-- 1261 release.txt
drwxr-xr-x - src
drwxr-xr-x - test