Add Merge.

Will merge queries maps from a list of *DotSql returning a new one.

dotsql.go

@@ -112,3 +112,20 @@ func LoadFromString(sql string) (*DotSql, error) {
 	buf := bytes.NewBufferString(sql)
 	return Load(buf)
 }
+
+// Merge takes one or more *DotSql and merge its queries
+// It's in-order, so the last source will override queries with the same name
+// in the previous arguments if any.
+func Merge(dots ...*DotSql) *DotSql {
+	queries := make(map[string]string)
+
+	for _, dot := range dots {
+		for k, v := range dot.QueryMap() {
+			queries[k] = v
+		}
+	}
+
+	return &DotSql{
+		queries: queries,
+	}
+}

dotsql_test.go

@@ -63,3 +63,43 @@ func TestQueries(t *testing.T) {
 		}
 	}
 }
+
+func TestMergeHaveBothQueries(t *testing.T) {
+	expectedQueryMap := map[string]string{
+		"query-a": "SELECT * FROM a",
+		"query-b": "SELECT * FROM b",
+	}
+
+	a, err := LoadFromString("--name: query-a\nSELECT * FROM a")
+	failIfError(t, err)
+
+	b, err := LoadFromString("--name: query-b\nSELECT * FROM b")
+	failIfError(t, err)
+
+	c := Merge(a, b)
+
+	got := c.QueryMap()
+	if len(got) != len(expectedQueryMap) {
+		t.Errorf("QueryMap() len (%d) differ from expected (%d)", len(got), len(expectedQueryMap))
+	}
+}
+
+func TestMergeTakesPresecendeFromLastArgument(t *testing.T) {
+	expectedQuery := "SELECT * FROM c"
+
+	a, err := LoadFromString("--name: query\nSELECT * FROM a")
+	failIfError(t, err)
+
+	b, err := LoadFromString("--name: query\nSELECT * FROM b")
+	failIfError(t, err)
+
+	c, err := LoadFromString("--name: query\nSELECT * FROM c")
+	failIfError(t, err)
+
+	x := Merge(a, b, c)
+
+	got := x.QueryMap()["query"]
+	if expectedQuery != got {
+		t.Errorf("Expected query: '%s', got: '%s'", expectedQuery, got)
+	}
+}