Bump libgit2 to 6777db8e834

carlosmn · carlosmn · commit b7985ebf85dd · 2019-12-10T20:04:34.000Z
This includes security fixes around NTFS alternate data streams.
diff --git a/vendor/libgit2 b/vendor/libgit2
@@ -1 +1 @@
-Subproject commit 08cfa43d0e1a9214a2f1239593686078e75e5636
+Subproject commit 6777db8e8343014d57c41b335e0c60af44d4e9f2
