Allow users with explicit read access to give approvals (#8382)

models/branches.go

 	}
 	protectBranch.MergeWhitelistUserIDs = whitelist
 
-	whitelist, err = updateUserWhitelist(repo, protectBranch.ApprovalsWhitelistUserIDs, opts.ApprovalsUserIDs)
+	whitelist, err = updateApprovalWhitelist(repo, protectBranch.ApprovalsWhitelistUserIDs, opts.ApprovalsUserIDs)
 	if err != nil {
 		return err
 	}
 	return false, nil
 }
 
+// updateApprovalWhitelist checks whether the user whitelist changed and returns a whitelist with
+// the users from newWhitelist which have explicit read or write access to the repo.
+func updateApprovalWhitelist(repo *Repository, currentWhitelist, newWhitelist []int64) (whitelist []int64, err error) {
+	hasUsersChanged := !util.IsSliceInt64Eq(currentWhitelist, newWhitelist)
+	if !hasUsersChanged {
+		return currentWhitelist, nil
+	}
+
+	whitelist = make([]int64, 0, len(newWhitelist))
+	for _, userID := range newWhitelist {
+		if reader, err := repo.IsReader(userID); err != nil {
+			return nil, err
+		} else if !reader {
+			continue
+		}
+		whitelist = append(whitelist, userID)
+	}
+
+	return
+}
+
 // updateUserWhitelist checks whether the user whitelist changed and returns a whitelist with
 // the users from newWhitelist which have write access to the repo.
 func updateUserWhitelist(repo *Repository, currentWhitelist, newWhitelist []int64) (whitelist []int64, err error) {

models/repo.go

 	return !repo.IsMirror
 }
 
+// GetReaders returns all users that have explicit read access or higher to the repository.
+func (repo *Repository) GetReaders() (_ []*User, err error) {
+	return repo.getUsersWithAccessMode(x, AccessModeRead)
+}
+
 // GetWriters returns all users that have write access to the repository.
 func (repo *Repository) GetWriters() (_ []*User, err error) {
 	return repo.getUsersWithAccessMode(x, AccessModeWrite)
 }
 
+// IsReader returns true if user has explicit read access or higher to the repository.
+func (repo *Repository) IsReader(userID int64) (bool, error) {
+	if repo.OwnerID == userID {
+		return true, nil
+	}
+	return x.Where("repo_id = ? AND user_id = ? AND mode >= ?", repo.ID, userID, AccessModeRead).Get(&Access{})
+}
+
 // getUsersWithAccessMode returns users that have at least given access mode to the repository.
 func (repo *Repository) getUsersWithAccessMode(e Engine, mode AccessMode) (_ []*User, err error) {
 	if err = repo.getOwner(e); err != nil {

routers/repo/setting_protected_branch.go

 		}
 	}
 
-	users, err := c.Repo.Repository.GetWriters()
+	users, err := c.Repo.Repository.GetReaders()
 	if err != nil {
-		c.ServerError("Repo.Repository.GetWriters", err)
+		c.ServerError("Repo.Repository.GetReaders", err)
 		return
 	}
 	c.Data["Users"] = users