t3404: decouple some test cases from outcomes of previous test cases
Originally, the `--preserve-merges` option of the `git rebase` command piggy-backed on top of the `--interactive` feature. For that reason, the early test cases were added to the very same test script that contains the `git rebase -i` tests: `t3404-rebase-interactive.sh`. However, since c42abfe7857 (rebase: introduce a dedicated backend for --preserve-merges, 2018-05-28), the `--preserve-merges` feature got its own backend, in preparation for converting the rest of the `--interactive` code to built-in code, written in C rather than shell. The reason why the `--preserve-merges` feature was not converted at the same time is that we have something much better now: `--rebase-merges`. That option intends to supersede `--preserve-merges`, and we will probably deprecate the latter soon. Once `--preserve-merges` has been deprecated for a good amount of time, it will be time to remove it, and along with it, its tests. In preparation for that, let's make the rest of the test cases in `t3404-rebase-interactive.sh` independent of the test cases dedicated to `--preserve-merges`. Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>