Update status and code index after changing the default branch (#27018)

Fix #26723 
Add `ChangeDefaultBranch` to the `notifier` interface and implement it
in `indexerNotifier`. So when changing the default branch,
`indexerNotifier` sends a message to the `indexer queue` to update the
index.

---------

Co-authored-by: techknowlogick <matti@mdranta.net>

2 files changed, 64 insertions, 50 deletions

diff --git a/routers/web/repo/setting/default_branch.go b/routers/web/repo/setting/default_branch.go
new file mode 100644
index 0000000000..f0aa1a89e7
--- /dev/null
+++ b/routers/web/repo/setting/default_branch.go
@@ -0,0 +1,64 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package setting
+
+import (
+	"net/http"
+
+	repo_model "code.gitea.io/gitea/models/repo"
+	"code.gitea.io/gitea/modules/context"
+	"code.gitea.io/gitea/modules/git"
+	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/setting"
+	"code.gitea.io/gitea/routers/web/repo"
+	notify_service "code.gitea.io/gitea/services/notify"
+)
+
+// SetDefaultBranchPost set default branch
+func SetDefaultBranchPost(ctx *context.Context) {
+	ctx.Data["Title"] = ctx.Tr("repo.settings.branches.update_default_branch")
+	ctx.Data["PageIsSettingsBranches"] = true
+
+	repo.PrepareBranchList(ctx)
+	if ctx.Written() {
+		return
+	}
+
+	repo := ctx.Repo.Repository
+
+	switch ctx.FormString("action") {
+	case "default_branch":
+		if ctx.HasError() {
+			ctx.HTML(http.StatusOK, tplBranches)
+			return
+		}
+
+		branch := ctx.FormString("branch")
+		if !ctx.Repo.GitRepo.IsBranchExist(branch) {
+			ctx.Status(http.StatusNotFound)
+			return
+		} else if repo.DefaultBranch != branch {
+			repo.DefaultBranch = branch
+			if err := ctx.Repo.GitRepo.SetDefaultBranch(branch); err != nil {
+				if !git.IsErrUnsupportedVersion(err) {
+					ctx.ServerError("SetDefaultBranch", err)
+					return
+				}
+			}
+			if err := repo_model.UpdateDefaultBranch(repo); err != nil {
+				ctx.ServerError("SetDefaultBranch", err)
+				return
+			}
+
+			notify_service.ChangeDefaultBranch(ctx, repo)
+		}
+
+		log.Trace("Repository basic settings updated: %s/%s", ctx.Repo.Owner.Name, repo.Name)
+
+		ctx.Flash.Success(ctx.Tr("repo.settings.update_settings_success"))
+		ctx.Redirect(setting.AppSubURL + ctx.Req.URL.EscapedPath())
+	default:
+		ctx.NotFound("", nil)
+	}
+}
diff --git a/routers/web/repo/setting/protected_branch.go b/routers/web/repo/setting/protected_branch.go
index 5bfdb8f515..e0f2294a14 100644
--- a/routers/web/repo/setting/protected_branch.go
+++ b/routers/web/repo/setting/protected_branch.go
@@ -14,12 +14,8 @@ import (
 	"code.gitea.io/gitea/models/organization"
 	"code.gitea.io/gitea/models/perm"
 	access_model "code.gitea.io/gitea/models/perm/access"
-	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/modules/base"
 	"code.gitea.io/gitea/modules/context"
-	"code.gitea.io/gitea/modules/git"
-	"code.gitea.io/gitea/modules/log"
-	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/web"
 	"code.gitea.io/gitea/routers/web/repo"
 	"code.gitea.io/gitea/services/forms"
@@ -53,52 +49,6 @@ func ProtectedBranchRules(ctx *context.Context) {
 	ctx.HTML(http.StatusOK, tplBranches)
 }
 
-// SetDefaultBranchPost set default branch
-func SetDefaultBranchPost(ctx *context.Context) {
-	ctx.Data["Title"] = ctx.Tr("repo.settings.branches.update_default_branch")
-	ctx.Data["PageIsSettingsBranches"] = true
-
-	repo.PrepareBranchList(ctx)
-	if ctx.Written() {
-		return
-	}
-
-	repo := ctx.Repo.Repository
-
-	switch ctx.FormString("action") {
-	case "default_branch":
-		if ctx.HasError() {
-			ctx.HTML(http.StatusOK, tplBranches)
-			return
-		}
-
-		branch := ctx.FormString("branch")
-		if !ctx.Repo.GitRepo.IsBranchExist(branch) {
-			ctx.Status(http.StatusNotFound)
-			return
-		} else if repo.DefaultBranch != branch {
-			repo.DefaultBranch = branch
-			if err := ctx.Repo.GitRepo.SetDefaultBranch(branch); err != nil {
-				if !git.IsErrUnsupportedVersion(err) {
-					ctx.ServerError("SetDefaultBranch", err)
-					return
-				}
-			}
-			if err := repo_model.UpdateDefaultBranch(repo); err != nil {
-				ctx.ServerError("SetDefaultBranch", err)
-				return
-			}
-		}
-
-		log.Trace("Repository basic settings updated: %s/%s", ctx.Repo.Owner.Name, repo.Name)
-
-		ctx.Flash.Success(ctx.Tr("repo.settings.update_settings_success"))
-		ctx.Redirect(setting.AppSubURL + ctx.Req.URL.EscapedPath())
-	default:
-		ctx.NotFound("", nil)
-	}
-}
-
 // SettingsProtectedBranch renders the protected branch setting page
 func SettingsProtectedBranch(c *context.Context) {
 	ruleName := c.FormString("rule_name")