Support pulling plugins by digest (#3803)

Previously `WithPlugins` only supported passing image URIs "by tag" --
e.g. `gcr.io/my-repo/my-image:v0.1.2`. With this commit, we add support
for pulling "by digest" -- e.g.
`gcr.io/my-repo/my-image@sha256:a75f9e8c3ced3943515f249597be389f8233e1258d289b11184796edceaa7dab`

Signed-off-by: Eric Fried <efried@redhat.com>

changelogs/unreleased/3803-2uasimojo

@@ -0,0 +1 @@
+Support pulling plugin images by digest

pkg/builder/container_builder.go

@@ -60,11 +60,18 @@ func getName(image string) string {
 		start = slashIndex + 1
 	}
 
-	// this removes the tag
-	colonIndex := strings.LastIndex(image, ":")
+	// If the image spec is by digest, remove the digest.
+	// If it is by tag, remove the tag.
+	// Otherwise (implicit :latest) leave it alone.
 	end := len(image)
-	if colonIndex > 0 {
-		end = colonIndex
+	atIndex := strings.LastIndex(image, "@")
+	if atIndex > 0 {
+		end = atIndex
+	} else {
+		colonIndex := strings.LastIndex(image, ":")
+		if colonIndex > 0 {
+			end = colonIndex
+		}
 	}
 
 	// https://github.com/distribution/distribution/blob/main/docs/spec/api.md#overview

pkg/builder/container_builder_test.go

@@ -87,6 +87,11 @@ func TestGetName(t *testing.T) {
 			image:    "projects.registry.vmware.com/tanzu.migrator/route-2-httpproxy:myTag",
 			expected: "tanzu-migrator-route-2-httpproxy",
 		},
+		{
+			name:     "pull by digest",
+			image:    "quay.io/vmware-tanzu/velero@sha256:a75f9e8c3ced3943515f249597be389f8233e1258d289b11184796edceaa7dab",
+			expected: "vmware-tanzu-velero",
+		},
 	}
 
 	for _, test := range tests {