feat: cleanup git repository before doing project backup

This can considerably reduce backup sizes for repos using squashing and
rebasing.

weblate/trans/backups.py

@@ -278,6 +278,11 @@ def backup_component(self, backupzip, component) -> None:
         # Store VCS repo in case it is present
         if component.is_repo_link:
             return
+
+        # Compact the repository
+        component.repo.compact()
+
+        # Actually perform the backup
         self.backup_dir(
             backupzip,
             component.full_path,

weblate/vcs/base.py

@@ -562,3 +562,6 @@ def get_remote_branch_name(self, branch: str | None = None) -> str:
 
     def list_remote_branches(self):
         return []
+
+    def compact(self) -> None:
+        return

weblate/vcs/git.py

@@ -566,6 +566,9 @@ def status(self):
 
         return "\n".join(result)
 
+    def compact(self) -> None:
+        self.execute(["gc"])
+
 
 class GitWithGerritRepository(GitRepository):
     name = "Gerrit"