Do not allow organisation owners add themselves as collaborator

routers/web/repo/setting.go

@@ -911,6 +911,23 @@ func CollaborationPost(ctx *context.Context) {
 		return
 	}
 
+	// find the owner team of the organization the repo belongs too and
+	// check if the user we're trying to add is an owner.
+	if ctx.Repo.Repository.Owner.IsOrganization() {
+		teams, err := organization.GetRepoTeams(ctx, ctx.Repo.Repository)
+		if err != nil {
+			ctx.ServerError("GetRepoTeams", err)
+			return
+		}
+
+		for _, team := range teams {
+			if team.IsOwnerTeam() && team.IsMember(u.ID) {
+				ctx.Redirect(setting.AppSubURL + ctx.Req.URL.EscapedPath())
+				return
+			}
+		}
+	}
+
 	if err = models.AddCollaborator(ctx.Repo.Repository, u); err != nil {
 		ctx.ServerError("AddCollaborator", err)
 		return