Add git commit advice

week1/02-grading-and-submission.md

@@ -37,7 +37,7 @@ haven't committed by writing:
 git status
 ```
 
-(If you get the error `Not a valid command: git`, it means you're inside `sbt`,
+(If you get the error `Not a valid command: git`, it means you're inside sbt,
 you can't run git from sbt itself, you need to open another terminal in the same
 directory)
 
@@ -55,6 +55,8 @@ good commit messages)
 git commit -am "My message"
 ```
 
+(It's good practice to commit your code regularly to document your changes)
+
 You can then synchronize your local git repository with the gitlab server by
 first running:
 ```shell