skip test headBranchSha != sha when PR is closed

Author: sillyguodong

routers/web/repo/pull.go

@@ -587,7 +587,7 @@ func PrepareViewPullInfo(ctx *context.Context, issue *issues_model.Issue) *git.C
 	ctx.Data["HeadBranchCommitID"] = headBranchSha
 	ctx.Data["PullHeadCommitID"] = sha
 
-	if pull.HeadRepo == nil || !headBranchExist {
+	if pull.HeadRepo == nil || !headBranchExist || (!pull.Issue.IsClosed && (headBranchSha != sha)) {
 		ctx.Data["IsPullRequestBroken"] = true
 		if pull.IsSameRepo() {
 			ctx.Data["HeadTarget"] = pull.HeadBranch