Show "delete branch" button on closed pull requests (#6570) (#6601)

* Show button to delete a pull request branch after a pull request has been closed (#6570)

Signed-off-by: Mario Lubenka <mario.lubenka@googlemail.com>

* Update routers/repo/pull.go

Co-Authored-By: saitho <mario.lubenka@googlemail.com>

routers/repo/issue.go

@@ -674,6 +674,7 @@ func ViewIssue(ctx *context.Context) {
 			PrepareMergedViewPullInfo(ctx, issue)
 		} else {
 			PrepareViewPullInfo(ctx, issue)
+			ctx.Data["DisableStatusChange"] = ctx.Data["IsPullRequestBroken"] == true && issue.IsClosed
 		}
 		if ctx.Written() {
 			return

routers/repo/pull.go

@@ -999,8 +999,8 @@ func CleanUpPullRequest(ctx *context.Context) {
 
 	pr := issue.PullRequest
 
-	// Allow cleanup only for merged PR
-	if !pr.HasMerged {
+	// Don't cleanup unmerged and unclosed PRs
+	if !pr.HasMerged && !issue.IsClosed {
 		ctx.NotFound("CleanUpPullRequest", nil)
 		return
 	}