Vendor continuity

Signed-off-by: Derek McGowan <derek@mcgstyle.net> (github: dmcgowan)

vendor/github.com/stevvooe/continuity/ioutils.go

@@ -0,0 +1,39 @@
+package continuity
+
+import (
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+)
+
+// atomicWriteFile writes data to a file by first writing to a temp
+// file and calling rename.
+func atomicWriteFile(filename string, r io.Reader, rf RegularFile) error {
+	f, err := ioutil.TempFile(filepath.Dir(filename), ".tmp-"+filepath.Base(filename))
+	if err != nil {
+		return err
+	}
+	err = os.Chmod(f.Name(), rf.Mode())
+	if err != nil {
+		f.Close()
+		return err
+	}
+	n, err := io.Copy(f, r)
+	if err == nil && n < rf.Size() {
+		f.Close()
+		return io.ErrShortWrite
+	}
+	if err != nil {
+		f.Close()
+		return err
+	}
+	if err := f.Sync(); err != nil {
+		f.Close()
+		return err
+	}
+	if err := f.Close(); err != nil {
+		return err
+	}
+	return os.Rename(f.Name(), filename)
+}