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

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

syft/source/sourceproviders/source_provider_config.go

@@ -0,0 +1,56 @@
+package sourceproviders
+
+import (
+	"crypto"
+
+	"github.com/anchore/stereoscope/pkg/image"
+	"github.com/anchore/syft/syft/source"
+)
+
+// Config is the uber-configuration for all Syft source providers
+type Config struct {
+	Platform         *image.Platform
+	Alias            source.Alias
+	RegistryOptions  *image.RegistryOptions
+	Exclude          source.ExcludeConfig
+	DigestAlgorithms []crypto.Hash
+	BasePath         string
+}
+
+func (c *Config) WithAlias(alias source.Alias) *Config {
+	c.Alias = alias
+	return c
+}
+
+func (c *Config) WithRegistryOptions(registryOptions *image.RegistryOptions) *Config {
+	c.RegistryOptions = registryOptions
+	return c
+}
+
+func (c *Config) WithPlatform(platform *image.Platform) *Config {
+	c.Platform = platform
+	return c
+}
+
+func (c *Config) WithExcludeConfig(excludeConfig source.ExcludeConfig) *Config {
+	c.Exclude = excludeConfig
+	return c
+}
+
+func (c *Config) WithDigestAlgorithms(algorithms ...crypto.Hash) *Config {
+	c.DigestAlgorithms = algorithms
+	return c
+}
+
+func (c *Config) WithBasePath(basePath string) *Config {
+	c.BasePath = basePath
+	return c
+}
+
+func DefaultConfig() *Config {
+	return &Config{
+		DigestAlgorithms: []crypto.Hash{
+			crypto.SHA256,
+		},
+	}
+}