Add portage support for Gentoo Linux (#1076)

Co-authored-by: Christopher Phillips <christopher.phillips@anchore.com>

schema/json/README.md

@@ -25,7 +25,7 @@ Given a version number format `MODEL.REVISION.ADDITION`:
 When adding a new `pkg.*Metadata` that is assigned to the `pkg.Package.Metadata` struct field it is important that a few things
 are done:
 
-- a new integration test case is added to `test/integration/pkg_cases_test.go` that exercises the new package type with the new metadata
+- a new integration test case is added to `test/integration/catalog_packages_cases_test.go` that exercises the new package type with the new metadata
 - the new metadata struct is added to the `artifactMetadataContainer` struct within `schema/json/generate.go`
 
 ## Generating a New Schema
@@ -36,4 +36,4 @@ Create the new schema by running `cd schema/json && go run generate.go` (note yo
 - If there is an existing schema for the given version and the new schema matches the existing schema, no action is taken
 - If there is an existing schema for the given version and the new schema **does not** match the existing schema, an error is shown indicating to increment the version appropriately (see the "Versioning" section)
 
-***Note: never delete a JSON schema and never change an existing JSON schema once it has been published in a release!*** Only add new schemas with a newly incremented version. All previous schema files must be stored in the `schema/json/` directory.
+***Note: never delete a JSON schema and never change an existing JSON schema once it has been published in a release!*** Only add new schemas with a newly incremented version. All previous schema files must be stored in the `schema/json/` directory.

schema/json/generate.go

@@ -27,19 +27,20 @@ can be extended to include specific package metadata struct shapes in the future
 // When a new package metadata definition is created it will need to be manually added here. The variable name does
 // not matter as long as it is exported.
 type artifactMetadataContainer struct {
-	Apk    pkg.ApkMetadata
-	Alpm   pkg.AlpmMetadata
-	Dpkg   pkg.DpkgMetadata
-	Gem    pkg.GemMetadata
-	Java   pkg.JavaMetadata
-	Npm    pkg.NpmPackageJSONMetadata
-	Python pkg.PythonPackageMetadata
-	Rpm    pkg.RpmdbMetadata
-	Cargo  pkg.CargoPackageMetadata
-	Go     pkg.GolangBinMetadata
-	Php    pkg.PhpComposerJSONMetadata
-	Dart   pkg.DartPubMetadata
-	Dotnet pkg.DotnetDepsMetadata
+	Apk     pkg.ApkMetadata
+	Alpm    pkg.AlpmMetadata
+	Dpkg    pkg.DpkgMetadata
+	Gem     pkg.GemMetadata
+	Java    pkg.JavaMetadata
+	Npm     pkg.NpmPackageJSONMetadata
+	Python  pkg.PythonPackageMetadata
+	Rpm     pkg.RpmdbMetadata
+	Cargo   pkg.CargoPackageMetadata
+	Go      pkg.GolangBinMetadata
+	Php     pkg.PhpComposerJSONMetadata
+	Dart    pkg.DartPubMetadata
+	Dotnet  pkg.DotnetDepsMetadata
+	Portage pkg.PortageMetadata
 }
 
 func main() {