osbuild: add ostree.deploy.container stage

Creates an org.osbuild.ostree.deploy.container stage.
Validates the options with a regular expression that matches the schema.
Takes a container as input.  Validates the length of the input
references to be exactly 1.

See osbuild/osbuild#1402

pkg/osbuild/ostree_deploy_container_stage.go

@@ -0,0 +1,67 @@
+package osbuild
+
+import (
+	"fmt"
+	"regexp"
+)
+
+const ostreeContainerTargetImgrefRegex = "^(ostree-remote-registry|ostree-image-signed|ostree-unverified-registry):.*$"
+
+// Options for the org.osbuild.ostree.deploy.container stage.
+type OSTreeDeployContainerStageOptions struct {
+
+	// Name of the stateroot to be used in the deployment
+	OsName string `json:"osname"`
+
+	// Additional kernel command line options
+	KernelOpts []string `json:"kernel_opts,omitempty"`
+
+	// Image ref used as the source of truth for updates
+	TargetImgref string `json:"target_imgref"`
+
+	// Identifier to locate the root file system (uuid or label)
+	Rootfs *Rootfs `json:"rootfs,omitempty"`
+
+	// Mount points of the final file system
+	Mounts []string `json:"mounts,omitempty"`
+}
+
+func (OSTreeDeployContainerStageOptions) isStageOptions() {}
+
+func (options OSTreeDeployContainerStageOptions) validate() error {
+	exp := regexp.MustCompile(ostreeContainerTargetImgrefRegex)
+	if !exp.MatchString(options.TargetImgref) {
+		return fmt.Errorf("'target_imgref' %q doesn't conform to schema (%s)", options.TargetImgref, exp.String())
+	}
+	return nil
+}
+
+type OSTreeDeployContainerInputs struct {
+	Images ContainersInput `json:"images"`
+}
+
+func (OSTreeDeployContainerInputs) isStageInputs() {}
+
+func (inputs OSTreeDeployContainerInputs) validate() error {
+	if ncontainers := inputs.Images.References.Len(); ncontainers != 1 {
+		return fmt.Errorf("stage requires exactly 1 input container (got %d)", ncontainers)
+	}
+	return nil
+}
+
+func NewOSTreeDeployContainerStage(options *OSTreeDeployContainerStageOptions, images ContainersInput) *Stage {
+	if err := options.validate(); err != nil {
+		panic(err)
+	}
+	inputs := OSTreeDeployContainerInputs{
+		Images: images,
+	}
+	if err := inputs.validate(); err != nil {
+		panic(err)
+	}
+	return &Stage{
+		Type:    "org.osbuild.ostree.deploy.container",
+		Options: options,
+		Inputs:  inputs,
+	}
+}