test: add basic integration tests

Signed-off-by: Justin Chadwell <me@jedevc.com>

vendor/github.com/containerd/continuity/fs/fstest/file_unix.go

@@ -0,0 +1,54 @@
+//go:build !windows
+// +build !windows
+
+/*
+   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 fstest
+
+import (
+	"path/filepath"
+	"time"
+
+	"github.com/containerd/continuity/sysx"
+	"golang.org/x/sys/unix"
+)
+
+// SetXAttr sets the xatter for the file
+func SetXAttr(name, key, value string) Applier {
+	return applyFn(func(root string) error {
+		path := filepath.Join(root, name)
+		return sysx.LSetxattr(path, key, []byte(value), 0)
+	})
+}
+
+// Lchtimes changes access and mod time of file without following symlink
+func Lchtimes(name string, atime, mtime time.Time) Applier {
+	return applyFn(func(root string) error {
+		path := filepath.Join(root, name)
+		at := unix.NsecToTimespec(atime.UnixNano())
+		mt := unix.NsecToTimespec(mtime.UnixNano())
+		utimes := [2]unix.Timespec{at, mt}
+		return unix.UtimesNanoAt(unix.AT_FDCWD, path, utimes[0:], unix.AT_SYMLINK_NOFOLLOW)
+	})
+}
+
+func Base() Applier {
+	return applyFn(func(root string) error {
+		// do nothing, as the base is not special
+		return nil
+	})
+}