fmt --upgrade -p: pin commit without events where the stored flow has it (#895 default change, rehearsal M1) #873

Part of #714 (dress rehearsal class M1).

Symptom

Since mendixlabs#895 (Aug 2026) a bare commit $X; means with events, Studio Pro's default (MDL067 notes it once per flow). Flows written by an older mxcli from the same scripts store commit $X without events (the pre-#895 meaning of a bare commit).

Re-running such a script therefore changes stored behaviour (handlers start running) — and when the commit is inside a loop, under mdl 1 the splice refuses the statement forever ("the Loop … changes inside its body"). In the rehearsal this hit 5 flows of mxcli-ledger (03, 13, 17). fmt --upgrade did nothing about it, because the script alone cannot know what is stored.

Repro (/home/vscode/rehearsal/repros/commit-default-in-loop.setup.mdl + .mdl):

-- setup: the flow as an older mxcli stored it
create or modify microflow MyFirstModule.Repro_CommitInLoop ($Items: List of MyFirstModule.Tx)
begin
  loop $T in $Items
  begin
    change $T (Amount = 0);
    commit $T without events;
  end loop;
end;
-- then, twice:
mdl 1;
create or modify microflow MyFirstModule.Repro_CommitInLoop ($Items: List of MyFirstModule.Tx)
begin
  loop $T in $Items
  begin
    change $T (Amount = 0);
    commit $T;
  end loop;
end;

Proposed fix

fmt --upgrade -p app.mpr: for a create or modify microflow|nanoflow whose stored flow commits a variable only without events where the script writes a bare commit $X, rewrite the statement to state the stored flag (commit $X without events), so the upgrade preserves what is stored and the re-run is Unchanged. Without -p, leave the script and print a note naming MDL067 and -p. An ambiguous case (the stored flow commits the variable both ways, or the script commits it more often than the stored flow) is left and reported.