Add some hardcoded mapping to deduce the right target branch for a project

This partially addresses #20 by introducing a relatively reasonable extension point and a hacky implementation for it (hardcoded values).

The logic will have to be properly implemented at some point.

reference_update_bot/update_references.py

@@ -822,13 +822,25 @@ def update_references(
     gitlab_br_name, gitlab_title = make_gitlab_mr_branch_name_and_title(mr_slot_meta)
     gitlab_title = f"{gitlab_title} based on {slot_name}/{latest_mr_slot_id}"
 
+    # FIXME: temporary hack to address https://gitlab.cern.ch/lhcb-rta/reference-update-bot/-/issues/20
+    #        while waiting for a proper fix
+    def target_branch_for_project_in_slot(project: str, slot: str) -> str:
+        # I could use args.target, but the actual logic should deduce the
+        # branch from the slot
+        branch = slot.replace("lhcb-", "").replace("-mr", "")
+        if branch == "2024-patches" and project in ("Boole", "Online"):
+            branch = "master"
+        elif branch == "sim10":
+            branch = "Sim10" if project == "Gauss" else "sim10-patches"
+        return branch
+
     projects_to_push = [
         create_ref_update_commit(
             projects_base_commits[proj],
             slot_name,
             latest_mr_slot_id,
             proj,
-            args.target,
+            target_branch_for_project_in_slot(proj, slot_name),
             plats_to_pull_refs,
             refs_to_update,
             new_refs,