Merge branch 'en/merge-ort-api-null-impl'

Preparation for a new merge strategy. * en/merge-ort-api-null-impl: merge,rebase,revert: select ort or recursive by config or environment fast-rebase: demonstrate merge-ort's API via new test-tool command merge-ort-wrappers: new convience wrappers to mimic the old merge API merge-ort: barebones API of new merge strategy with empty implementation