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

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

examples/source_detection/main.go

@@ -1,10 +1,15 @@
 package main
 
 import (
+	"context"
 	"encoding/json"
 	"os"
 
+	"github.com/anchore/go-collections"
+	"github.com/anchore/stereoscope"
+	"github.com/anchore/syft/syft"
 	"github.com/anchore/syft/syft/source"
+	"github.com/anchore/syft/syft/source/sourceproviders"
 )
 
 /*
@@ -28,18 +33,18 @@ import (
 const defaultImage = "alpine:3.19"
 
 func main() {
-	detection, err := source.Detect(
-		imageReference(),
-		source.DetectConfig{
-			DefaultImageSource: "docker",
-		},
-	)
+	userInput := imageReference()
 
-	if err != nil {
-		panic(err)
+	// parse the scheme against the known set of schemes
+	schemeSource, newUserInput := stereoscope.ExtractSchemeSource(userInput, allSourceTags()...)
+
+	// set up the GetSourceConfig
+	getSourceCfg := syft.DefaultGetSourceConfig()
+	if schemeSource != "" {
+		getSourceCfg = getSourceCfg.WithSources(schemeSource)
+		userInput = newUserInput
 	}
-
-	src, err := detection.NewSource(source.DefaultDetectionSourceConfig())
+	src, err := syft.GetSource(context.Background(), userInput, getSourceCfg)
 
 	if err != nil {
 		panic(err)
@@ -60,3 +65,7 @@ func imageReference() string {
 	}
 	return defaultImage
 }
+
+func allSourceTags() []string {
+	return collections.TaggedValueSet[source.Provider]{}.Join(sourceproviders.All("", nil)...).Tags()
+}