Create and document diff package.

pkg/diff/directory.go

@@ -0,0 +1,38 @@
+package diff
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+)
+
+// directory represents a new temp directory and lets one create files in it.
+type directory struct {
+	n string
+}
+
+// newDirectory makes a directory instance holding a new temp directory on disk.
+// The directory name is the given prefix following by a random string.
+func newDirectory(prefix string) (*directory, error) {
+	name, err := ioutil.TempDir("", prefix+"-")
+	if err != nil {
+		return nil, err
+	}
+
+	return &directory{n: name}, nil
+}
+
+// newFile creates a new file in the directory.
+func (d *directory) newFile(name string) (*os.File, error) {
+	return os.OpenFile(filepath.Join(d.n, name), os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0700)
+}
+
+// delete removes the directory recursively.
+func (d *directory) delete() error {
+	return os.RemoveAll(d.n)
+}
+
+// name is the name of the directory.
+func (d *directory) name() string {
+	return d.n
+}