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

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

syft/internal/testutil/chdir.go

@@ -0,0 +1,26 @@
+package testutil
+
+import (
+	"os"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func Chdir(t *testing.T, dir string) {
+	t.Helper()
+
+	wd, err := os.Getwd()
+	if err != nil {
+		t.Fatalf("unable to get working directory: %v", err)
+	}
+
+	err = os.Chdir(dir)
+	if err != nil {
+		t.Fatalf("unable to chdir to '%s': %v", dir, err)
+	}
+
+	t.Cleanup(func() {
+		require.NoError(t, os.Chdir(wd))
+	})
+}