Update User.NumRepos atomically in createRepository (#7493)

The update call on the user call races if there is more than one
repository creation concurrently, leading to incorrect count of
repos. Split things in two, so that we call the update for last
visibility (which isn't problematic if it races, since it can only
ever be best-effort anyway). This way we can atomically increment
the count of repos.

Author: emonty

models/repo.go

@@ -1306,13 +1306,17 @@ func createRepository(e *xorm.Session, doer, u *User, repo *Repository) (err err
 		return err
 	}
 
-	u.NumRepos++
 	// Remember visibility preference.
 	u.LastRepoVisibility = repo.IsPrivate
-	if err = updateUser(e, u); err != nil {
+	if err = updateUserCols(e, u, "last_repo_visibility"); err != nil {
 		return fmt.Errorf("updateUser: %v", err)
 	}
 
+	if _, err = e.Incr("num_repos").ID(u.ID).Update(new(User)); err != nil {
+		return fmt.Errorf("increment user total_repos: %v", err)
+	}
+	u.NumRepos++
+
 	// Give access to all members in owner team.
 	if u.IsOrganization() {
 		t, err := u.getOwnerTeam(e)