Fix Dockerfile parser (#459)

Co-authored-by: CrazyMax <crazy-max@users.noreply.github.com>

pkg/dockerfile/image_test.go

@@ -0,0 +1,34 @@
+package dockerfile_test
+
+import (
+	"testing"
+
+	"github.com/crazy-max/diun/v4/pkg/dockerfile"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestFromImages(t *testing.T) {
+	c, err := dockerfile.New(dockerfile.Options{
+		Filename: "./fixtures/valid.Dockerfile",
+	})
+	require.NoError(t, err)
+	require.NotNil(t, c)
+
+	img, err := c.FromImages()
+	require.NoError(t, err)
+	require.NotNil(t, img)
+	require.Equal(t, 3, len(img))
+
+	assert.Equal(t, "alpine:3.14", img[0].Name)
+	assert.Equal(t, 5, img[0].Line)
+	assert.Equal(t, []string{"diun.platform=linux/amd64"}, img[0].Comments)
+
+	assert.Equal(t, "crazymax/yasu", img[1].Name)
+	assert.Equal(t, 10, img[1].Line)
+	assert.Equal(t, []string{"diun.watch_repo=true", "diun.max_tags=10", "diun.platform=linux/amd64"}, img[1].Comments)
+
+	assert.Equal(t, "crazymax/docker:20.10.6", img[2].Name)
+	assert.Equal(t, 15, img[2].Line)
+	assert.Equal(t, []string{"diun.watch_repo=true", "diun.include_tags=^\\d+\\.\\d+\\.\\d+$", "diun.platform=linux/amd64"}, img[2].Comments)
+}