Update git2 package

Cargo.lock

@@ -1,5 +1,7 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
+version = 3
+
 [[package]]
 name = "ansi_term"
 version = "0.12.1"
@@ -90,9 +92,9 @@ dependencies = [
 
 [[package]]
 name = "git2"
-version = "0.13.18"
+version = "0.13.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b483c6c2145421099df1b4efd50e0f6205479a072199460eff852fa15e5603c7"
+checksum = "d9831e983241f8c5591ed53f17d874833e2fa82cac2625f3888c50cbfe136cba"
 dependencies = [
  "bitflags",
  "libc",
@@ -151,9 +153,9 @@ checksum = "9385f66bf6105b241aa65a61cb923ef20efc665cb9f9bb50ac2f0c4b7f378d41"
 
 [[package]]
 name = "libgit2-sys"
-version = "0.12.19+1.1.0"
+version = "0.12.21+1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f322155d574c8b9ebe991a04f6908bb49e68a79463338d24a43d6274cb6443e6"
+checksum = "86271bacd72b2b9e854c3dcfb82efd538f15f870e4c11af66900effb462f6825"
 dependencies = [
  "cc",
  "libc",