feat: add support to use issue template from registry index for pack yank

internal/registry/github.go

@@ -4,7 +4,10 @@ import (
 	"bytes"
 	"fmt"
 	"net/url"
+	"os"
 	"os/exec"
+	"path/filepath"
+	"regexp"
 	"strings"
 	"text/template"
 
@@ -18,13 +21,29 @@ type GithubIssue struct {
 	Body  string
 }
 
-func CreateGithubIssue(b Buildpack) (GithubIssue, error) {
-	titleTemplate, err := template.New("buildpack").Parse(GithubIssueTitleTemplate)
+// CreateGithubIssue creates a GitHub issue from a buildpack. If registryRoot is provided,
+// it will attempt to load both title and body templates from the registry-index repository,
+// falling back to hardcoded templates if the file doesn't exist.
+// Returns the issue and a boolean indicating whether templates were loaded from the registry.
+func CreateGithubIssue(b Buildpack, registryRoot ...string) (GithubIssue, error) {
+	titleTemplateStr := GithubIssueTitleTemplate
+	bodyTemplateStr := GithubIssueBodyTemplate
+
+	// Try to load templates from registry if root is provided
+	if len(registryRoot) > 0 && registryRoot[0] != "" {
+		if title, body, err := loadTemplatesFromRegistry(registryRoot[0], b.Yanked); err == nil {
+			titleTemplateStr = title
+			bodyTemplateStr = body
+		}
+		// Silently fall back to hardcoded templates if loading fails
+	}
+
+	titleTemplate, err := template.New("buildpack").Parse(titleTemplateStr)
 	if err != nil {
 		return GithubIssue{}, err
 	}
 
-	bodyTemplate, err := template.New("buildpack").Parse(GithubIssueBodyTemplate)
+	bodyTemplate, err := template.New("buildpack").Parse(bodyTemplateStr)
 	if err != nil {
 		return GithubIssue{}, err
 	}
@@ -47,6 +66,72 @@ func CreateGithubIssue(b Buildpack) (GithubIssue, error) {
 	}, nil
 }
 
+// loadTemplatesFromRegistry loads both title and body templates from the registry-index repository.
+// It parses the YAML frontmatter to extract the title and extracts the body from the markdown content.
+func loadTemplatesFromRegistry(registryRoot string, yanked bool) (string, string, error) {
+	var templatePath string
+	if yanked {
+		templatePath = ".github/ISSUE_TEMPLATE/yank-buildpack.md"
+	} else {
+		templatePath = ".github/ISSUE_TEMPLATE/add-buildpack.md"
+	}
+
+	fullPath := filepath.Join(registryRoot, templatePath)
+	content, err := os.ReadFile(fullPath)
+	if err != nil {
+		return "", "", err
+	}
+
+	contentStr := string(content)
+
+	// Parse YAML frontmatter to extract title
+	titleTemplate, bodyTemplate, err := parseTemplateFile(contentStr)
+	if err != nil {
+		return "", "", err
+	}
+
+	// Convert placeholders to Go template syntax
+	titleTemplate = convertPlaceholdersToGoTemplate(titleTemplate)
+	bodyTemplate = convertPlaceholdersToGoTemplate(bodyTemplate)
+
+	return titleTemplate, bodyTemplate, nil
+}
+
+// parseTemplateFile parses a GitHub issue template file with YAML frontmatter
+// and returns the title template and body template.
+func parseTemplateFile(content string) (string, string, error) {
+	// Split frontmatter from body
+	parts := strings.SplitN(content, "---\n", 3)
+	if len(parts) < 3 {
+		return "", "", errors.New("invalid template format: missing YAML frontmatter")
+	}
+
+	frontmatter := parts[1]
+	body := parts[2]
+
+	// Extract title from frontmatter
+	titleMatch := regexp.MustCompile(`(?m)^title:\s*(.+)$`).FindStringSubmatch(frontmatter)
+	if len(titleMatch) < 2 {
+		return "", "", errors.New("invalid template format: missing title in frontmatter")
+	}
+	titleTemplate := strings.TrimSpace(titleMatch[1])
+	// Remove quotes if present
+	titleTemplate = strings.Trim(titleTemplate, `"'`)
+
+	return titleTemplate, strings.TrimSpace(body), nil
+}
+
+// convertPlaceholdersToGoTemplate converts template placeholders like {BUILDPACK_ID} and {VERSION}
+// to Go template syntax like {{.Namespace}}/{{.Name}} and {{.Version}}.
+func convertPlaceholdersToGoTemplate(templateStr string) string {
+	// Replace {BUILDPACK_ID} with {{.Namespace}}/{{.Name}}
+	templateStr = strings.ReplaceAll(templateStr, "{BUILDPACK_ID}", "{{.Namespace}}/{{.Name}}")
+	// Replace {VERSION} with {{.Version}}
+	templateStr = strings.ReplaceAll(templateStr, "{VERSION}", "{{.Version}}")
+
+	return templateStr
+}
+
 func CreateBrowserCmd(browserURL, os string) (*exec.Cmd, error) {
 	_, err := url.ParseRequestURI(browserURL)
 	if err != nil {

internal/registry/registry_cache.go

@@ -36,11 +36,7 @@ type Cache struct {
 }
 
 const GithubIssueTitleTemplate = "{{ if .Yanked }}YANK{{ else }}ADD{{ end }} {{.Namespace}}/{{.Name}}@{{.Version}}"
-const GithubIssueBodyTemplate = `
-id = "{{.Namespace}}/{{.Name}}"
-version = "{{.Version}}"
-{{ if .Yanked }}{{ else if .Address }}addr = "{{.Address}}"{{ end }}
-`
+const GithubIssueBodyTemplate = "```\nid = \"{{.Namespace}}/{{.Name}}\"\nversion = \"{{.Version}}\"\n{{ if .Yanked }}yank = true\n{{ end }}{{ if .Address }}addr = \"{{.Address}}\"\n{{ end }}```"
 const GitCommitTemplate = `{{ if .Yanked }}YANK{{else}}ADD{{end}} {{.Namespace}}/{{.Name}}@{{.Version}}`
 
 // Entry is a list of buildpacks stored in a registry

pkg/client/yank_buildpack.go

@@ -4,6 +4,7 @@ import (
 	"net/url"
 	"runtime"
 
+	"github.com/buildpacks/pack/internal/config"
 	"github.com/buildpacks/pack/internal/registry"
 )
 
@@ -36,14 +37,39 @@ func (c *Client) YankBuildpack(opts YankBuildpackOptions) error {
 		Yanked:    opts.Yank,
 	}
 
-	issue, err := registry.CreateGithubIssue(buildpack)
+	// Try to get registry cache root to load template from registry-index
+	var registryRoot string
+	home, err := config.PackHome()
+	if err == nil {
+		registryCache, err := registry.NewRegistryCache(c.logger, home, opts.URL)
+		if err == nil {
+			// Initialize the cache if needed (this will clone/refresh the registry)
+			if err := registryCache.Initialize(); err == nil {
+				// Refresh to get latest template
+				_ = registryCache.Refresh()
+				registryRoot = registryCache.Root
+			}
+		} else {
+			c.logger.Warnf("Error initializing registry cache: %s", err)
+		}
+	}
+
+	issue, err := registry.CreateGithubIssue(buildpack, registryRoot)
 	if err != nil {
 		return err
 	}
 
 	params := url.Values{}
 	params.Add("title", issue.Title)
 	params.Add("body", issue.Body)
+	// Add template parameter when we have a registry root (GitHub will use the template if it exists)
+	if registryRoot != "" {
+		if opts.Yank {
+			params.Add("template", "yank-buildpack.md")
+		} else {
+			params.Add("template", "add-buildpack.md")
+		}
+	}
 	issueURL.RawQuery = params.Encode()
 
 	c.logger.Debugf("Open URL in browser: %s", issueURL)