Bump libgit2 to 1573acb

vmg · vmg · commit f33e4dd86c47 · 2015-08-13T14:39:13.000+02:00
diff --git a/vendor/libgit2 b/vendor/libgit2
@@ -1 +1 @@
-Subproject commit 98f7bd289dfb172473b7d7353d4b0f0b09c67937
+Subproject commit 1573acbbd9023b5c447caa7489f9579d8ffc810e
