feat: add --from flag, refactor source providers (#2610)

Signed-off-by: Keith Zantow <kzantow@gmail.com>

syft/source/stereoscopesource/image_source_provider.go

@@ -0,0 +1,61 @@
+package stereoscopesource
+
+import (
+	"context"
+
+	"github.com/anchore/go-collections"
+	"github.com/anchore/stereoscope"
+	"github.com/anchore/stereoscope/pkg/image"
+	"github.com/anchore/syft/syft/source"
+)
+
+const ImageTag = "image"
+
+type ProviderConfig struct {
+	StereoscopeImageProviderConfig stereoscope.ImageProviderConfig
+	Exclude                        source.ExcludeConfig
+	Alias                          source.Alias
+}
+
+type stereoscopeImageSourceProvider struct {
+	stereoscopeProvider image.Provider
+	cfg                 ProviderConfig
+}
+
+var _ source.Provider = (*stereoscopeImageSourceProvider)(nil)
+
+func (l stereoscopeImageSourceProvider) Name() string {
+	return l.stereoscopeProvider.Name()
+}
+
+func (l stereoscopeImageSourceProvider) Provide(ctx context.Context) (source.Source, error) {
+	img, err := l.stereoscopeProvider.Provide(ctx)
+	if err != nil {
+		return nil, err
+	}
+	cfg := ImageConfig{
+		Reference:       l.cfg.StereoscopeImageProviderConfig.UserInput,
+		Platform:        l.cfg.StereoscopeImageProviderConfig.Platform,
+		RegistryOptions: &l.cfg.StereoscopeImageProviderConfig.Registry,
+		Exclude:         l.cfg.Exclude,
+		Alias:           l.cfg.Alias,
+	}
+	if err != nil {
+		return nil, err
+	}
+	return New(img, cfg), nil
+}
+
+func Providers(cfg ProviderConfig) []collections.TaggedValue[source.Provider] {
+	stereoscopeProviders := collections.TaggedValueSet[source.Provider]{}
+	providers := stereoscope.ImageProviders(cfg.StereoscopeImageProviderConfig)
+	for _, provider := range providers {
+		var sourceProvider source.Provider = stereoscopeImageSourceProvider{
+			stereoscopeProvider: provider.Value,
+			cfg:                 cfg,
+		}
+		stereoscopeProviders = append(stereoscopeProviders,
+			collections.NewTaggedValue(sourceProvider, append([]string{provider.Value.Name(), ImageTag}, provider.Tags...)...))
+	}
+	return stereoscopeProviders
+}