Improve onboard template: per-issue content-aware welcome comments

- fetchIssueDetail now gets both subject and description
- renderComment substitutes {subject}, {description}, {number}, {login}
- defaultTemplate includes issue summary for targeted guidance
- dry-run preview shows the full rendered comment

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shortcuts/onboard/onboarding.go

@@ -25,7 +25,7 @@ func Shortcuts() []*common.Shortcut {
 			Flags: []common.Flag{
 				{Name: "issues", Short: "i", Usage: "Comma-separated issue numbers (e.g. 1,3,7)"},
 				{Name: "tag", Short: "t", Usage: "Tag name to match (comma-separated)", Default: "good first issue,help wanted"},
-				{Name: "template", Usage: "Custom welcome message template (use {login} for @mention)"},
+				{Name: "template", Usage: "Custom welcome message template ({login}, {number}, {subject}, {description})"},
 			},
 			DryRun:     true,
 			DryRunHint: dryRunHint,
@@ -96,11 +96,11 @@ func runWelcomeByIssueNumbers(ctx *common.RuntimeContext, issueArg string) error
 
 	var issues []issueInfo
 	for _, num := range issueNums {
-		subject, err := fetchIssueSubject(ctx, num)
+		info, err := fetchIssueDetail(ctx, num)
 		if err != nil {
 			return fmt.Errorf("获取 issue #%d 失败: %w", num, err)
 		}
-		issues = append(issues, issueInfo{number: num, subject: subject})
+		issues = append(issues, info)
 	}
 
 	return processIssues(ctx, issues)
@@ -127,18 +127,20 @@ func parseIssueNumbers(s string) ([]int, error) {
 	return nums, nil
 }
 
-// fetchIssueSubject fetches a single issue's subject by number.
-func fetchIssueSubject(ctx *common.RuntimeContext, issueNumber int) (string, error) {
+// fetchIssueDetail fetches a single issue's subject and description by number.
+func fetchIssueDetail(ctx *common.RuntimeContext, issueNumber int) (issueInfo, error) {
 	path := fmt.Sprintf("/v1/%s/%s/issues/%d", ctx.Owner, ctx.Repo, issueNumber)
 	env, err := ctx.CallAPIWithQuery("GET", path, nil)
 	if err != nil {
-		return "", err
+		return issueInfo{}, err
 	}
 	data, _ := env.Data.(map[string]interface{})
-	if subj := getString(data, "subject"); subj != "" {
-		return subj, nil
+	subj := getString(data, "subject")
+	if subj == "" {
+		subj = fmt.Sprintf("issue #%d", issueNumber)
 	}
-	return fmt.Sprintf("issue #%d", issueNumber), nil
+	desc := getString(data, "description")
+	return issueInfo{number: issueNumber, subject: subj, description: desc}, nil
 }
 
 // processIssues handles the common issue processing loop used by both
@@ -146,7 +148,7 @@ func fetchIssueSubject(ctx *common.RuntimeContext, issueNumber int) (string, err
 func processIssues(ctx *common.RuntimeContext, issues []issueInfo) error {
 	tmpl := ctx.Arg("template")
 	if tmpl == "" {
-		tmpl = defaultTemplate(ctx.Owner, ctx.Repo)
+		tmpl = ""
 	}
 
 	type result struct {
@@ -162,7 +164,11 @@ func processIssues(ctx *common.RuntimeContext, issues []issueInfo) error {
 			continue
 		}
 
+		// Render per-issue message with issue-specific variables.
+		body := renderComment(ctx, issue, tmpl)
+
 		if ctx.IsDryRun() {
+			fmt.Printf("\n--- 预览 #%d \"%s\" ---\n%s\n---\n", issue.number, issue.subject, body)
 			proceed, err := common.ConfirmAction(ctx)
 			if err != nil {
 				return err
@@ -173,7 +179,7 @@ func processIssues(ctx *common.RuntimeContext, issues []issueInfo) error {
 			}
 		}
 
-		if err := addComment(ctx, issue.number, tmpl); err != nil {
+		if err := addComment(ctx, issue.number, body); err != nil {
 			results = append(results, result{issue.number, "error", err.Error()})
 		} else {
 			results = append(results, result{issue.number, "added", fmt.Sprintf("#%d \"%s\" — 已添加引导评论", issue.number, issue.subject)})
@@ -247,8 +253,9 @@ func tagNamesList(tags map[string]int) []string {
 }
 
 type issueInfo struct {
-	number  int
-	subject string
+	number      int
+	subject     string
+	description string
 }
 
 func fetchTaggedIssues(ctx *common.RuntimeContext, tagIDs []string) ([]issueInfo, error) {
@@ -313,30 +320,55 @@ func hasWelcomeComment(ctx *common.RuntimeContext, issueNumber int) bool {
 }
 
 func addComment(ctx *common.RuntimeContext, issueNumber int, body string) error {
-	body = strings.ReplaceAll(body, "{login}", ctx.Owner)
 	path := fmt.Sprintf("/v1/%s/%s/issues/%d/journals", ctx.Owner, ctx.Repo, issueNumber)
 	payload := map[string]interface{}{"notes": marker + "\n\n" + body}
 	_, err := ctx.CallAPI("POST", path, payload)
 	return err
 }
 
-// defaultTemplate returns the default onboarding message.
-func defaultTemplate(owner, repo string) string {
+// renderComment renders the comment body for a specific issue.
+// It uses the --template if provided, otherwise generates an issue-aware default.
+func renderComment(ctx *common.RuntimeContext, issue issueInfo, customTmpl string) string {
+	tmpl := customTmpl
+	if tmpl == "" {
+		tmpl = defaultTemplate(ctx.Owner, ctx.Repo, issue)
+	}
+	body := strings.NewReplacer(
+		"{login}", ctx.Owner,
+		"{number}", strconv.Itoa(issue.number),
+		"{subject}", issue.subject,
+		"{description}", issue.description,
+	).Replace(tmpl)
+	return body
+}
+
+// defaultTemplate returns an issue-aware onboarding message.
+func defaultTemplate(owner, repo string, issue issueInfo) string {
+	summary := issue.subject
+	if len(issue.description) > 200 {
+		summary = issue.description[:200] + "..."
+	} else if issue.description != "" {
+		summary = issue.description
+	}
 	return fmt.Sprintf(`## 欢迎贡献！:wave:
 
-感谢你对 [%s/%s](https://www.gitlink.org.cn/%s/%s) 的关注。这个 issue 适合新手参与，以下是快速上手指南：
+感谢你对 [%s/%s](https://www.gitlink.org.cn/%s/%s) 的关注。
 
-### 参与步骤
+### :bulb: 关于本 Issue：{subject}
+
+%s
+
+### :rocket: 参与步骤
 1. **Fork 仓库** 并克隆到本地
 2. 创建新分支：` + "`git checkout -b fix/issue-{number}`" + `
-3. 修改代码并提交
+3. 参照上方 issue 描述修改代码
 4. 推送到你的 Fork 后创建 Pull Request
 
-### 注意事项
+### :memo: 注意事项
 - 请先阅读 [CONTRIBUTING.md](https://www.gitlink.org.cn/%s/%s/src/master/CONTRIBUTING.md)（如有）
-- 如遇到问题，欢迎在 issue 评论区留言
+- 如有疑问，欢迎在评论区留言讨论
 
-期待你的 PR！`, owner, repo, owner, repo, owner, repo)
+期待你的 PR！`, owner, repo, owner, repo, summary, owner, repo)
 }
 
 func getString(m map[string]interface{}, key string) string {