Update libgit2 to v0.27.4

tiennou · tiennou · commit 52826550bbf6 · 2018-08-11T00:05:18.000+02:00
diff --git a/External/libgit2 b/External/libgit2
@@ -1 +1 @@
-Subproject commit 8d36dc62ba1b5d7deb66b6f982e005ddbc2ce343
+Subproject commit 8b89f362a34fcccdf1c6c5f3445895b71d9c6d56
