Merge branch 'js/rebase-p-tests'

In preparation to the day when we can deprecate and remove the "rebase -p", make sure we can skip and later remove tests for it. * js/rebase-p-tests: tests: optionally skip `git rebase -p` tests t3418: decouple test cases from a previous `rebase -p` test case t3404: decouple some test cases from outcomes of previous test cases