clone: also cleanup checkout with git gc

ofborg/src/clone.rs

@@ -147,6 +147,13 @@ pub trait GitClonable {
             .stdout(Stdio::null())
             .status()?;
 
+        debug!("git gc");
+        Command::new("git")
+            .arg("gc")
+            .current_dir(self.clone_to())
+            .stdout(Stdio::null())
+            .status()?;
+
         lock.unlock();
 
         Ok(())