repostate: allow "commit" in "goto --merge" state

Summary:
I didn't think this was useful, but there is an eden integration test that makes a commit after resolving merge conflicts but before running "goto --continue".

Let's just re-allow this without thinking too hard.

Reviewed By: genevievehelsel

Differential Revision: D52051317

fbshipit-source-id: fa45410762f0d733443c163c89f7b0d58f99a9c6

eden/scm/lib/workingcopy/repostate/src/command_state.rs

@@ -105,8 +105,7 @@ static STATES: &[State] = &[
         command: "goto",
         description: "goto --merge in progress",
         state_file: "updatemergestate",
-        // In Python, we allowed "commit", but I don't think that makes sense (anymore).
-        allows: &[],
+        allows: &[Operation::Commit],
         proceed: "goto --continue",
         abort: "goto --clean",
         abort_lossy: true,