Mark PR reviews as stale at push and allow to dismiss stale approvals (#9532)

Fix #5997.

If a push causes the patch/diff of a PR towards target branch to change, all existing reviews for the PR will be set and shown as stale.
New branch protection option to dismiss stale approvals are added.
To show that a review is not based on the latest PR changes, an hourglass is shown

models/migrations/migrations.go

@@ -290,6 +290,8 @@ var migrations = []Migration{
 	NewMigration("Extend TrackedTimes", extendTrackedTimes),
 	// v117 -> v118
 	NewMigration("Add block on rejected reviews branch protection", addBlockOnRejectedReviews),
+	// v118 -> v119
+	NewMigration("Add commit id and stale to reviews", addReviewCommitAndStale),
 }
 
 // Migrate database to current version

models/migrations/v118.go

@@ -0,0 +1,26 @@
+// Copyright 2019 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 (
+	"xorm.io/xorm"
+)
+
+func addReviewCommitAndStale(x *xorm.Engine) error {
+	type Review struct {
+		CommitID string `xorm:"VARCHAR(40)"`
+		Stale    bool   `xorm:"NOT NULL DEFAULT false"`
+	}
+
+	type ProtectedBranch struct {
+		DismissStaleApprovals bool `xorm:"NOT NULL DEFAULT false"`
+	}
+
+	// Old reviews will have commit ID set to "" and not stale
+	if err := x.Sync2(new(Review)); err != nil {
+		return err
+	}
+	return x.Sync2(new(ProtectedBranch))
+}