Add git pull to the instructions

week1/02-grading-and-submission.md

@@ -52,9 +52,18 @@ git commit -am "My message"
 ```
 
 You can then synchronize your local git repository with the gitlab server by
-running:
+first running:
 ```shell
- git push
+ git pull
+```
+
+This will merge in your local repository any change we made to the assignment
+(we only change assignments to fix critical bugs found after it's been released,
+so most of the time this will not do anything).
+
+Finally, you can push your changes to gitlab:
+```shell
+git push
 ```
 
 Note that there are also graphical user interfaces to interact with git, for