Restrict permission check on repositories and fix some problems (#5314)

* fix units permission problems

* fix some bugs and merge LoadUnits to repoAssignment

* refactor permission struct and add some copyright heads

* remove unused codes

* fix routes units check

* improve permission check

* add unit tests for permission

* fix typo

* fix tests

* fix some routes

* fix api permission check

* improve permission check

* fix some permission check

* fix tests

* fix tests

* improve some permission check

* fix some permission check

* refactor AccessLevel

* fix bug

* fix tests

* fix tests

* fix tests

* fix AccessLevel

* rename CanAccess

* fix tests

* fix comment

* fix bug

* add missing unit for test repos

* fix bug

* rename some functions

* fix routes check

routers/repo/release.go

@@ -1,4 +1,5 @@
 // Copyright 2014 The Gogs Authors. All rights reserved.
+// Copyright 2018 The Gitea Authors. All rights reserved.
 // Use of this source code is governed by a MIT-style
 // license that can be found in the LICENSE file.
 
@@ -65,8 +66,11 @@ func Releases(ctx *context.Context) {
 		limit = 10
 	}
 
+	writeAccess := ctx.Repo.CanWrite(models.UnitTypeReleases)
+	ctx.Data["CanCreateRelease"] = writeAccess
+
 	opts := models.FindReleasesOptions{
-		IncludeDrafts: ctx.Repo.IsWriter(),
+		IncludeDrafts: writeAccess,
 		IncludeTags:   true,
 	}