sql: Begin cleanup of code

internal/component/sql/snapshot.go

@@ -0,0 +1,21 @@
+package sql
+
+import (
+	"io"
+
+	"github.com/tkw1536/goprogram/stream"
+)
+
+// Snapshot makes a backup of the sql database into dest.
+func (sql SQL) Snapshot(io stream.IOStream, dest io.Writer, database string) error {
+	io = io.Streams(dest, nil, nil, 0).NonInteractive()
+
+	code, err := sql.Stack(sql.Environment).Exec(io, "sql", "mysqldump", "--databases", database)
+	if err != nil {
+		return err
+	}
+	if code != 0 {
+		return errSQLBackup
+	}
+	return nil
+}