Use repo as of renderctx's member rather than a repoPath on metas (#29222)

Use a `gitrepo.Repository` in the markup's RenderContext but not store
the repository's path.

models/issues/comment_code.go

@@ -113,7 +113,8 @@ func findCodeComments(ctx context.Context, opts FindCommentsOptions, issue *Issu
 
 		var err error
 		if comment.RenderedContent, err = markdown.RenderString(&markup.RenderContext{
-			Ctx: ctx,
+			Ctx:  ctx,
+			Repo: issue.Repo,
 			Links: markup.Links{
 				Base: issue.Repo.Link(),
 			},

models/repo/repo.go

@@ -472,10 +472,9 @@ func (repo *Repository) MustOwner(ctx context.Context) *user_model.User {
 func (repo *Repository) ComposeMetas(ctx context.Context) map[string]string {
 	if len(repo.RenderingMetas) == 0 {
 		metas := map[string]string{
-			"user":     repo.OwnerName,
-			"repo":     repo.Name,
-			"repoPath": repo.RepoPath(),
-			"mode":     "comment",
+			"user": repo.OwnerName,
+			"repo": repo.Name,
+			"mode": "comment",
 		}
 
 		unit, err := repo.GetUnit(ctx, unit.TypeExternalTracker)