obsolete: add operation metadata to rebase/amend/histedit obsmarkers By recording what operation created the obsmarker, we can show very intuitive messages to the user in various UIs. For instance, log output could have messages like "Amended as XXX" to show why a commit is old and has an 'x' on it. @ ac28e3 durham / First commit | | o d4afe7 durham | | Second commit | | | x 8e9a5d (Amended as ac28e3) durham |/ First commit |