chore(deps): cleanup go.mod a little bit (#136)

* Upgrade docker to v19.03.7

* go mod vendor

* golangci-lint 1.23.8

vendor/github.com/containerd/continuity/fs/du.go

@@ -0,0 +1,38 @@
+/*
+   Copyright The containerd Authors.
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+*/
+
+package fs
+
+import "context"
+
+// Usage of disk information
+type Usage struct {
+	Inodes int64
+	Size   int64
+}
+
+// DiskUsage counts the number of inodes and disk usage for the resources under
+// path.
+func DiskUsage(ctx context.Context, roots ...string) (Usage, error) {
+	return diskUsage(ctx, roots...)
+}
+
+// DiffUsage counts the numbers of inodes and disk usage in the
+// diff between the 2 directories. The first path is intended
+// as the base directory and the second as the changed directory.
+func DiffUsage(ctx context.Context, a, b string) (Usage, error) {
+	return diffUsage(ctx, a, b)
+}