Bump libgit2 to maintenance v0.26

implausible · implausible · commit cdfd81a9a556 · 2017-07-25T10:11:26.000-07:00
diff --git a/vendor/libgit2 b/vendor/libgit2
@@ -1 +1 @@
-Subproject commit 9e76f2c72bb562aba6f72b95216bc4e885a46551
+Subproject commit 3c1308d8c1afa74d5da76ff1d3b2106d352ed36f
