chore: only comment if it doesn't already exist

pkg/plugins/trigger/pull-request.go

@@ -255,10 +255,25 @@ func welcomeMsgForDraftPR(spc scmProviderClient, trigger *plugins.Trigger, pr sc
 		}
 	}
 
-	if err := spc.CreateComment(org, repo, pr.Number, true, comment); err != nil {
+	comments, err := spc.ListPullRequestComments(org, repo, pr.Number)
+	if err != nil {
 		errors = append(errors, err)
 	}
 
+	toComment := true
+	for _, c := range comments {
+		if c.Body == comment {
+			toComment = false
+			break
+		}
+	}
+
+	if toComment {
+		if err := spc.CreateComment(org, repo, pr.Number, true, comment); err != nil {
+			errors = append(errors, err)
+		}
+	}
+
 	if len(errors) > 0 {
 		return errorutil.NewAggregate(errors...)
 	}

pkg/plugins/trigger/trigger.go

@@ -125,6 +125,7 @@ type scmProviderClient interface {
 	GetPullRequest(org, repo string, number int) (*scm.PullRequest, error)
 	GetRef(org, repo, ref string) (string, error)
 	CreateComment(owner, repo string, number int, pr bool, comment string) error
+	ListPullRequestComments(org, repo string, number int) ([]*scm.Comment, error)
 	ListIssueComments(owner, repo string, issue int) ([]*scm.Comment, error)
 	CreateStatus(org, repo, ref string, s *scm.StatusInput) (*scm.Status, error)
 	GetCombinedStatus(org, repo, ref string) (*scm.CombinedStatus, error)