Simple file versioning (fixes #218)

osutil/osutil.go

@@ -0,0 +1,18 @@
+package osutil
+
+import (
+	"os"
+	"runtime"
+)
+
+func Rename(from, to string) error {
+	if runtime.GOOS == "windows" {
+		os.Chmod(to, 0666) // Make sure the file is user writeable
+		err := os.Remove(to)
+		if err != nil && !os.IsNotExist(err) {
+			return err
+		}
+	}
+	defer os.Remove(from) // Don't leave a dangling temp file in case of rename error
+	return os.Rename(from, to)
+}