Add thv skill builds command to list locally-built OCI artifacts (#4499)

Author: samuv

cmd/thv/app/skill_builds.go

@@ -0,0 +1,82 @@
+// SPDX-FileCopyrightText: Copyright 2025 Stacklok, Inc.
+// SPDX-License-Identifier: Apache-2.0
+
+package app
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"text/tabwriter"
+
+	"github.com/spf13/cobra"
+
+	"github.com/stacklok/toolhive/pkg/skills"
+)
+
+var skillBuildsFormat string
+
+var skillBuildsCmd = &cobra.Command{
+	Use:   "builds",
+	Short: "List locally-built skill artifacts",
+	Long:  `List all locally-built OCI skill artifacts stored in the local OCI store.`,
+	PreRunE: chainPreRunE(
+		ValidateFormat(&skillBuildsFormat),
+	),
+	RunE: skillBuildsCmdFunc,
+}
+
+func init() {
+	skillCmd.AddCommand(skillBuildsCmd)
+
+	AddFormatFlag(skillBuildsCmd, &skillBuildsFormat)
+}
+
+func skillBuildsCmdFunc(cmd *cobra.Command, _ []string) error {
+	c := newSkillClient(cmd.Context())
+
+	builds, err := c.ListBuilds(cmd.Context())
+	if err != nil {
+		return formatSkillError("list builds", err)
+	}
+
+	switch skillBuildsFormat {
+	case FormatJSON:
+		if builds == nil {
+			builds = []skills.LocalBuild{}
+		}
+		data, err := json.MarshalIndent(builds, "", "  ")
+		if err != nil {
+			return fmt.Errorf("failed to marshal JSON: %w", err)
+		}
+		fmt.Println(string(data))
+	default:
+		if len(builds) == 0 {
+			fmt.Println("No locally-built skill artifacts found")
+			return nil
+		}
+		printSkillBuildsText(builds)
+	}
+
+	return nil
+}
+
+func printSkillBuildsText(builds []skills.LocalBuild) {
+	w := tabwriter.NewWriter(os.Stdout, 0, 0, 3, ' ', 0)
+	_, _ = fmt.Fprintln(w, "TAG\tDIGEST\tNAME\tVERSION")
+
+	for _, b := range builds {
+		digest := b.Digest
+		if len(digest) > 19 {
+			digest = digest[:19] + "..."
+		}
+		_, _ = fmt.Fprintf(w, "%s\t%s\t%s\t%s\n",
+			b.Tag,
+			digest,
+			b.Name,
+			b.Version,
+		)
+	}
+
+	_ = w.Flush()
+}