docker: add git to extraPath

When building a docker container from git, docker was missing the git
binary in $PATH.

pkgs/applications/virtualization/docker/default.nix

@@ -1,7 +1,7 @@
 { stdenv, lib, fetchFromGitHub, makeWrapper, removeReferencesTo, pkgconfig
 , go-md2man, go, containerd, runc, docker-proxy, tini, libtool
 , sqlite, iproute, lvm2, systemd
-, btrfs-progs, iptables, e2fsprogs, xz, utillinux, xfsprogs
+, btrfs-progs, iptables, e2fsprogs, xz, utillinux, xfsprogs, git
 , procps, libseccomp
 }:
 
@@ -123,7 +123,7 @@ rec {
 
     outputs = ["out" "man"];
 
-    extraPath = optionals (stdenv.isLinux) (makeBinPath [ iproute iptables e2fsprogs xz xfsprogs procps utillinux ]);
+    extraPath = optionals (stdenv.isLinux) (makeBinPath [ iproute iptables e2fsprogs xz xfsprogs procps utillinux git ]);
 
     installPhase = optionalString (stdenv.isLinux) ''
       install -Dm755 ./components/engine/bundles/dynbinary-daemon/dockerd $out/libexec/docker/dockerd