Sync gitea app path for git hooks and authorized keys when starting (#17335)

Gitea writes its own AppPath into git hook scripts. If Gitea's AppPath changes, then the git push will fail.

This PR:

* Introduce an AppState module, it can persist app states into database
* During GlobalInit, Gitea will check if the current AppPath is the same as last one. If they don't match, Gitea will sync git hooks.
* Refactor some code to make them more clear.
* Also, "Detect if gitea binary's name changed" #11341 is related, we call models.RewriteAllPublicKeys to update ssh authorized_keys file

models/appstate/appstate.go

@@ -0,0 +1,57 @@
+// Copyright 2021 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.
+
+package appstate
+
+import (
+	"context"
+
+	"code.gitea.io/gitea/models/db"
+)
+
+// AppState represents a state record in database
+// if one day we would make Gitea run as a cluster,
+// we can introduce a new field `Scope` here to store different states for different nodes
+type AppState struct {
+	ID       string `xorm:"pk varchar(200)"`
+	Revision int64
+	Content  string `xorm:"LONGTEXT"`
+}
+
+func init() {
+	db.RegisterModel(new(AppState))
+}
+
+// SaveAppStateContent saves the app state item to database
+func SaveAppStateContent(key, content string) error {
+	return db.WithTx(func(ctx context.Context) error {
+		eng := db.GetEngine(ctx)
+		// try to update existing row
+		res, err := eng.Exec("UPDATE app_state SET revision=revision+1, content=? WHERE id=?", content, key)
+		if err != nil {
+			return err
+		}
+		rows, _ := res.RowsAffected()
+		if rows != 0 {
+			// the existing row is updated, so we can return
+			return nil
+		}
+		// if no existing row, insert a new row
+		_, err = eng.Insert(&AppState{ID: key, Content: content})
+		return err
+	})
+}
+
+// GetAppStateContent gets an app state from database
+func GetAppStateContent(key string) (content string, err error) {
+	e := db.GetEngine(db.DefaultContext)
+	appState := &AppState{ID: key}
+	has, err := e.Get(appState)
+	if err != nil {
+		return "", err
+	} else if !has {
+		return "", nil
+	}
+	return appState.Content, nil
+}

models/migrations/migrations.go

@@ -352,6 +352,8 @@ var migrations = []Migration{
 	NewMigration("Add issue content history table", addTableIssueContentHistory),
 	// v199 -> v200
 	NewMigration("Add remote version table", addRemoteVersionTable),
+	// v200 -> v201
+	NewMigration("Add table app_state", addTableAppState),
 }
 
 // GetCurrentDBVersion returns the current db version

models/migrations/v200.go

@@ -0,0 +1,23 @@
+// Copyright 2021 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.
+
+package migrations
+
+import (
+	"fmt"
+
+	"xorm.io/xorm"
+)
+
+func addTableAppState(x *xorm.Engine) error {
+	type AppState struct {
+		ID       string `xorm:"pk varchar(200)"`
+		Revision int64
+		Content  string `xorm:"LONGTEXT"`
+	}
+	if err := x.Sync2(new(AppState)); err != nil {
+		return fmt.Errorf("Sync2: %v", err)
+	}
+	return nil
+}