Update JOJ3 Configuration Schema

JOJ3-Configuration-Schema.md

@@ -7,6 +7,22 @@ Levels:
 - assignment: homework or project (no meta config needed at that level)
 - task: exercise or milestone
 
+## Commit message and course-joj repo tree 
+
+Commit messages must follow conventional commits format: `type[scope]: message`.  We use `scope` to track the exact task which is being worked on.
+
+Basic rules:
+- health check is **always** run first
+- all non JOJ stages are run on each push
+- JOJ is only triggered if the message is `joj` or `joj` appears in the message **TBD**
+
+Scope usage:
+- `scope` must match joj config tree (`home/tt/.config/joj` subtree in `course-joj` repo), eg. if tree is `h1/ex2` the `scope` must be `h1/ex2`, if tree is `hw4/1` then scope is also `hw4/1`.
+- if a scope is invalid then return a warning containing the list of valid scopes and exit nicely (either this is a typo, or this an exercise that do not require coding)
+- as health check must always be run, `scope` should be checked after it
+
+
+
 ## Repo level
 
 Teaching team info, eg. useful to check who triggered a grading.