Apply suggestions from code review

Co-authored-by: zeripath <[email protected]>

Author: justusbunsi

models/pull.go

@@ -217,16 +217,16 @@ func (pr *PullRequest) GetDefaultMergeMessage() string {
 		return ""
 	}
 
-	issueReference := fmt.Sprintf("#%d", pr.Issue.Index)
+	issueReference := "#"
 	if pr.BaseRepo.UnitEnabled(UnitTypeExternalTracker) {
-		issueReference = fmt.Sprintf("!%d", pr.Issue.Index)
+		issueReference = "!"
 	}
 
 	if pr.BaseRepoID == pr.HeadRepoID {
-		return fmt.Sprintf("Merge pull request '%s' (%s) from %s into %s", pr.Issue.Title, issueReference, pr.HeadBranch, pr.BaseBranch)
+		return fmt.Sprintf("Merge pull request '%s' (%s%d) from %s into %s", pr.Issue.Title, issueReference, pr.Issue.Index, pr.HeadBranch, pr.BaseBranch)
 	}
 
-	return fmt.Sprintf("Merge pull request '%s' (%s) from %s:%s into %s", pr.Issue.Title, issueReference, pr.HeadRepo.FullName(), pr.HeadBranch, pr.BaseBranch)
+	return fmt.Sprintf("Merge pull request '%s' (%s%d) from %s:%s into %s", pr.Issue.Title, issueReference, pr.Issue.Index, pr.HeadRepo.FullName(), pr.HeadBranch, pr.BaseBranch)
 }
 
 // ReviewCount represents a count of Reviews