Detect broken git hooks (#29494)

Detect broken git hooks by checking if the commit id of branches in DB
is the same with the git repo.

It can help #29338 #28277 and maybe more issues.

Users could complain about actions, webhooks, and activities not
working, but they were not aware that it is caused by broken git hooks
unless they could see a warning.

<img width="1348" alt="image"
src="https://github.com/go-gitea/gitea/assets/9418365/2b92a46d-7f1d-4115-bef4-9f970bd695da">


It should be merged after #29493. Otherwise, users could see a ephemeral
warning after committing and opening the repo home page immediately.

And it also waits for #29495, since the doc link (the anchor part) will
be updated.

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

options/locale/locale_en-US.ini

@@ -2643,6 +2643,7 @@ find_file.no_matching = No matching file found
 error.csv.too_large = Can't render this file because it is too large.
 error.csv.unexpected = Can't render this file because it contains an unexpected character in line %d and column %d.
 error.csv.invalid_field_count = Can't render this file because it has a wrong number of fields in line %d.
+error.broken_git_hook = Git hooks of this repository seem to be broken. Please follow the <a target="_blank" rel="noreferrer" href="%s">documentation</a> to fix them, then push some commits to refresh the status.
 
 [graphs]
 component_loading = Loading %s...

routers/web/repo/view.go

@@ -998,6 +998,8 @@ func renderHomeCode(ctx *context.Context) {
 		return
 	}
 
+	checkOutdatedBranch(ctx)
+
 	checkCitationFile(ctx, entry)
 	if ctx.Written() {
 		return
@@ -1064,6 +1066,31 @@ func renderHomeCode(ctx *context.Context) {
 	ctx.HTML(http.StatusOK, tplRepoHome)
 }
 
+func checkOutdatedBranch(ctx *context.Context) {
+	if !(ctx.Repo.IsAdmin() || ctx.Repo.IsOwner()) {
+		return
+	}
+
+	// get the head commit of the branch since ctx.Repo.CommitID is not always the head commit of `ctx.Repo.BranchName`
+	commit, err := ctx.Repo.GitRepo.GetBranchCommit(ctx.Repo.BranchName)
+	if err != nil {
+		log.Error("GetBranchCommitID: %v", err)
+		// Don't return an error page, as it can be rechecked the next time the user opens the page.
+		return
+	}
+
+	dbBranch, err := git_model.GetBranch(ctx, ctx.Repo.Repository.ID, ctx.Repo.BranchName)
+	if err != nil {
+		log.Error("GetBranch: %v", err)
+		// Don't return an error page, as it can be rechecked the next time the user opens the page.
+		return
+	}
+
+	if dbBranch.CommitID != commit.ID.String() {
+		ctx.Flash.Warning(ctx.Tr("repo.error.broken_git_hook", "https://docs.gitea.com/help/faq#push-hook--webhook--actions-arent-running"), true)
+	}
+}
+
 // RenderUserCards render a page show users according the input template
 func RenderUserCards(ctx *context.Context, total int, getter func(opts db.ListOptions) ([]*user_model.User, error), tpl base.TplName) {
 	page := ctx.FormInt("page")