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

modules/auth/repo_form.go

@@ -172,6 +172,7 @@ type ProtectBranchForm struct {
 	ApprovalsWhitelistUsers  string
 	ApprovalsWhitelistTeams  string
 	BlockOnRejectedReviews   bool
+	DismissStaleApprovals    bool
 }
 
 // Validate validates the fields
@@ -456,12 +457,13 @@ func (f *MergePullRequestForm) Validate(ctx *macaron.Context, errs binding.Error
 
 // CodeCommentForm form for adding code comments for PRs
 type CodeCommentForm struct {
-	Content  string `binding:"Required"`
-	Side     string `binding:"Required;In(previous,proposed)"`
-	Line     int64
-	TreePath string `form:"path" binding:"Required"`
-	IsReview bool   `form:"is_review"`
-	Reply    int64  `form:"reply"`
+	Content        string `binding:"Required"`
+	Side           string `binding:"Required;In(previous,proposed)"`
+	Line           int64
+	TreePath       string `form:"path" binding:"Required"`
+	IsReview       bool   `form:"is_review"`
+	Reply          int64  `form:"reply"`
+	LatestCommitID string
 }
 
 // Validate validates the fields
@@ -471,8 +473,9 @@ func (f *CodeCommentForm) Validate(ctx *macaron.Context, errs binding.Errors) bi
 
 // SubmitReviewForm for submitting a finished code review
 type SubmitReviewForm struct {
-	Content string
-	Type    string `binding:"Required;In(approve,comment,reject)"`
+	Content  string
+	Type     string `binding:"Required;In(approve,comment,reject)"`
+	CommitID string
 }
 
 // Validate validates the fields