Fix ignored login on compare (#12476) (#12478)

Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

routers/routes/routes.go

@@ -713,7 +713,7 @@ func RegisterRoutes(m *macaron.Macaron) {
 			m.Get("/:id", repo.MilestoneIssuesAndPulls)
 		}, reqRepoIssuesOrPullsReader, context.RepoRef())
 		m.Combo("/compare/*", repo.MustBeNotEmpty, reqRepoCodeReader, repo.SetEditorconfigIfExists).
-			Get(repo.SetDiffViewStyle, repo.CompareDiff).
+			Get(ignSignIn, repo.SetDiffViewStyle, repo.CompareDiff).
 			Post(reqSignIn, context.RepoMustNotBeArchived(), reqRepoPullsReader, repo.MustAllowPulls, bindIgnErr(auth.CreateIssueForm{}), repo.CompareAndPullRequestPost)
 	}, context.RepoAssignment(), context.UnitTypes())