refactor(image): add image reference interface

- Add image.Reference interface and SimpleReference implementation as
  parameters of image.Registry methods (in place of strings)
- Refactor image.Registry tests into suite
- Add registry implementation notes
- Remove buildah from builds (Note: should be re-added once it's
  complete)

Author: njhale

.gitignore

@@ -454,5 +454,10 @@ bin
 # Ignore vscode
 .vscode
 
-# Igore apprclient meta
+# Ignore apprclient meta
 pkg/apprclient/openapi/git_push.sh
+
+# Never ignore testdata
+!pkg/**/testdata/**
+!test/**testdata/**
+

go.mod

@@ -3,40 +3,50 @@ module github.com/operator-framework/operator-registry
 go 1.13
 
 require (
+	github.com/Microsoft/hcsshim v0.8.7 // indirect
 	github.com/antihax/optional v0.0.0-20180407024304-ca021399b1a6
 	github.com/blang/semver v3.5.0+incompatible
 	github.com/containerd/containerd v1.3.2
 	github.com/containerd/continuity v0.0.0-20200228182428-0f16d7a0959c // indirect
-	github.com/containers/buildah v1.14.3
 	github.com/docker/cli v0.0.0-20200130152716-5d0cf8839492
 	github.com/docker/distribution v2.7.1+incompatible
 	github.com/docker/docker v1.4.2-0.20200203170920-46ec8731fbce
+	github.com/docker/docker-credential-helpers v0.6.3 // indirect
 	github.com/docker/go-events v0.0.0-20190806004212-e31b211e4f1c // indirect
+	github.com/docker/go-metrics v0.0.1 // indirect
+	github.com/docker/libtrust v0.0.0-20160708172513-aabc10ec26b7 // indirect
 	github.com/ghodss/yaml v1.0.0
 	github.com/gogo/protobuf v1.3.1 // indirect
 	github.com/golang-migrate/migrate/v4 v4.6.2
 	github.com/golang/mock v1.3.1
 	github.com/golang/protobuf v1.3.2
+	github.com/google/go-cmp v0.4.0 // indirect
+	github.com/gorilla/mux v1.7.4 // indirect
 	github.com/grpc-ecosystem/grpc-health-probe v0.2.1-0.20181220223928-2bf0a5b182db
+	github.com/imdario/mergo v0.3.8 // indirect
 	github.com/mattn/go-sqlite3 v1.10.0
 	github.com/maxbrunsfeld/counterfeiter/v6 v6.2.2
 	github.com/morikuni/aec v1.0.0 // indirect
 	github.com/onsi/ginkgo v1.12.0
 	github.com/onsi/gomega v1.9.0
 	github.com/opencontainers/image-spec v1.0.2-0.20190823105129-775207bd45b6
+	github.com/opencontainers/runc v1.0.0-rc9 // indirect
+	github.com/opencontainers/runtime-spec v0.1.2-0.20190618234442-a950415649c7 // indirect
 	github.com/operator-framework/api v0.1.1
 	github.com/otiai10/copy v1.0.2
 	github.com/phayes/freeport v0.0.0-20180830031419-95f893ade6f2
 	github.com/pkg/errors v0.9.1
 	github.com/sirupsen/logrus v1.4.2
 	github.com/spf13/cobra v0.0.6
 	github.com/stretchr/testify v1.5.1
-	go.etcd.io/bbolt v1.3.3
+	go.etcd.io/bbolt v1.3.4
+	golang.org/x/crypto v0.0.0-20200220183623-bac4c82f6975 // indirect
 	golang.org/x/mod v0.2.0
 	golang.org/x/net v0.0.0-20191028085509-fe3aa8a45271
 	golang.org/x/oauth2 v0.0.0-20190604053449-0f29369cfe45
 	golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e // indirect
 	google.golang.org/grpc v1.24.0
+	gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 // indirect
 	gopkg.in/yaml.v2 v2.2.8
 	k8s.io/api v0.17.3
 	k8s.io/apiextensions-apiserver v0.17.3