add request review from specific reviewers feature in pull request (#10756)

* add request review feature in pull request

add a way to notify specific reviewers to review like github , by add  or delet a  special type
review . The acton is  is similar to Assign ,  so many code reuse the function and items of
Assignee, but the meaning and result is different.

The Permission style is is similar to github, that only writer can add a review request from Reviewers,
but the poster can recall and remove a review request after a reviwer has revied even if he don't have
Write Premission. only manager , the poster and reviewer of a request review can remove it.

The reviewers can be requested to review contain all readers for private repo , for public, contain
all writers and watchers.

The offical Review Request will block merge if Reject can block it.

an other change: add ui otify for Assignees.

Co-authored-by: guillep2k <18600385+guillep2k@users.noreply.github.com>
Co-authored-by: Lauris BH <lauris@nix.lv>

Signed-off-by: a1012112796 <1012112796@qq.com>

* new change

* add placeholder string

* do some changes follow #10238 to add review requests num on lists also
change icon for review requests to eye

Co-authored-by: Lauris BH <lauris@nix.lv>

models/repo.go

@@ -622,6 +622,64 @@ func (repo *Repository) GetAssignees() (_ []*User, err error) {
 	return repo.getAssignees(x)
 }
 
+func (repo *Repository) getReviewersPrivate(e Engine, doerID, posterID int64) (users []*User, err error) {
+	users = make([]*User, 0, 20)
+
+	if err = e.
+		SQL("SELECT * FROM `user` WHERE id in (SELECT user_id FROM `access` WHERE repo_id = ? AND mode >= ? AND user_id NOT IN ( ?, ?)) ORDER BY name",
+			repo.ID, AccessModeRead,
+			doerID, posterID).
+		Find(&users); err != nil {
+		return nil, err
+	}
+
+	return users, nil
+}
+
+func (repo *Repository) getReviewersPublic(e Engine, doerID, posterID int64) (_ []*User, err error) {
+
+	users := make([]*User, 0)
+
+	const SQLCmd = "SELECT * FROM `user` WHERE id IN ( " +
+		"SELECT user_id FROM `access` WHERE repo_id = ? AND mode >= ? AND user_id NOT IN ( ?, ?) " +
+		"UNION " +
+		"SELECT user_id FROM `watch` WHERE repo_id = ? AND user_id NOT IN ( ?, ?) AND mode IN (?, ?) " +
+		") ORDER BY name"
+
+	if err = e.
+		SQL(SQLCmd,
+			repo.ID, AccessModeRead, doerID, posterID,
+			repo.ID, doerID, posterID, RepoWatchModeNormal, RepoWatchModeAuto).
+		Find(&users); err != nil {
+		return nil, err
+	}
+
+	return users, nil
+}
+
+func (repo *Repository) getReviewers(e Engine, doerID, posterID int64) (users []*User, err error) {
+	if err = repo.getOwner(e); err != nil {
+		return nil, err
+	}
+
+	if repo.IsPrivate ||
+		(repo.Owner.IsOrganization() && repo.Owner.Visibility == api.VisibleTypePrivate) {
+		users, err = repo.getReviewersPrivate(x, doerID, posterID)
+	} else {
+		users, err = repo.getReviewersPublic(x, doerID, posterID)
+	}
+	return
+}
+
+// GetReviewers get all users can be requested to review
+// for private rpo , that return all users that have read access or higher to the repository.
+// but for public rpo, that return all users that have write access or higher to the repository,
+// and all repo watchers.
+// TODO: may be we should hava a busy choice for users to block review request to them.
+func (repo *Repository) GetReviewers(doerID, posterID int64) (_ []*User, err error) {
+	return repo.getReviewers(x, doerID, posterID)
+}
+
 // GetMilestoneByID returns the milestone belongs to repository by given ID.
 func (repo *Repository) GetMilestoneByID(milestoneID int64) (*Milestone, error) {
 	return GetMilestoneByRepoID(repo.ID, milestoneID)