assets/utils: Validate sub-projects in isGitRepoUrl function

Previously URL of type https://forge.example.org/user/project/sub-project/ were not validated by the isGitRepoUrl function.

Related to #2331 (closed)

---

Migrated from D2878 (view on Phabricator)

cypress/integration/origin-save.spec.js

 /**
- * Copyright (C) 2019  The Software Heritage developers
+ * Copyright (C) 2019-2020  The Software Heritage developers
  * See the AUTHORS file at the top-level directory of this distribution
  * License: GNU Affero General Public License version 3, or any later version
  * See top-level LICENSE file for more information
@@ -88,6 +88,19 @@ describe('Origin Save Tests', function() {
     });
   });
 
+  it('should validate gitlab subproject url', function() {
+    const gitlabSubProjectUrl = 'https://gitlab.com/user/project/sub/';
+    const originSaveUrl = this.Urls.origin_save_request('git', gitlabSubProjectUrl);
+    stubSaveRequest(originSaveUrl, 'git', 'accepted',
+                    gitlabSubProjectUrl, 'not yet scheduled');
+
+    makeOriginSaveRequest('git', gitlabSubProjectUrl);
+
+    cy.wait('@saveRequest').then(() => {
+      checkAlertVisible('success', saveCodeMsg['success']);
+    });
+  });
+
   it('should display warning message when pending', function() {
     stubSaveRequest(this.originSaveUrl, origin.type, 'pending',
                     origin.url, 'not created');