Add a simple way to rename branch like gh (#15870)

- Update default branch if needed
- Update protected branch if needed
- Update all not merged pull request base branch name
- Rename git branch
- Record this rename work and auto redirect for old branch on ui

Signed-off-by: a1012112796 <1012112796@qq.com>
Co-authored-by: delvh <dev.lh@web.de>

routers/web/web.go

@@ -612,6 +612,7 @@ func RegisterRoutes(m *web.Route) {
 				m.Combo("/*").Get(repo.SettingsProtectedBranch).
 					Post(bindIgnErr(forms.ProtectBranchForm{}), context.RepoMustNotBeArchived(), repo.SettingsProtectedBranchPost)
 			}, repo.MustBeNotEmpty)
+			m.Post("/rename_branch", bindIgnErr(forms.RenameBranchForm{}), context.RepoMustNotBeArchived(), repo.RenameBranchPost)
 
 			m.Group("/tags", func() {
 				m.Get("", repo.Tags)