Don't use an instance of VCS when isn't needed

readthedocs/builds/models.py

@@ -203,7 +203,7 @@ def vcs_url(self):
         if self.slug == STABLE:
             slug_url = self.ref
         elif self.slug == LATEST:
-            slug_url = self.project.default_branch or self.project.vcs_repo().fallback_branch
+            slug_url = self.project.get_default_branch()
         else:
             slug_url = self.slug
 
@@ -250,9 +250,7 @@ def commit_name(self):
         # LATEST is special as it is usually a branch but does not contain the
         # name in verbose_name.
         if self.slug == LATEST:
-            if self.project.default_branch:
-                return self.project.default_branch
-            return self.project.vcs_repo().fallback_branch
+            return self.project.get_default_branch()
 
         if self.slug == STABLE:
             if self.type == BRANCH:

readthedocs/projects/models.py

@@ -465,7 +465,7 @@ def save(self, *args, **kwargs):  # pylint: disable=arguments-differ
         except Exception:
             log.exception('failed to update static metadata')
         try:
-            branch = self.default_branch or self.vcs_repo().fallback_branch
+            branch = self.get_default_branch()
             if not self.versions.filter(slug=LATEST).exists():
                 self.versions.create_latest(identifier=branch)
         except Exception:
@@ -840,7 +840,7 @@ def vcs_repo(
         # ``version.slug`` instead of a ``Version`` instance (I prefer an
         # instance here)
 
-        backend = backend_cls.get(self.repo_type)
+        backend = self.vcs_class()
         if not backend:
             repo = None
         else:
@@ -850,6 +850,14 @@ def vcs_repo(
             )
         return repo
 
+    def vcs_class(self):
+        """
+        Get the class used for VCS operations.
+
+        This is useful when doing operations that don't need to have the repository on disk.
+        """
+        return backend_cls.get(self.repo_type)
+
     def git_service_class(self):
         """Get the service class for project. e.g: GitHubService, GitLabService."""
         from readthedocs.oauth.services import registry
@@ -1080,7 +1088,7 @@ def get_default_branch(self):
         """Get the version representing 'latest'."""
         if self.default_branch:
             return self.default_branch
-        return self.vcs_repo().fallback_branch
+        return self.vcs_class().fallback_branch
 
     def add_subproject(self, child, alias=None):
         subproject, __ = ProjectRelationship.objects.get_or_create(

readthedocs/projects/tasks.py

@@ -124,7 +124,7 @@ def sync_repo(self, environment):
         if not os.path.exists(self.project.doc_path):
             os.makedirs(self.project.doc_path)
 
-        if not self.project.vcs_repo():
+        if not self.project.vcs_class():
             raise RepositoryError(
                 _('Repository type "{repo_type}" unknown').format(
                     repo_type=self.project.repo_type,