rebase: enable multidest by default This was intended to be done by D470. But there was a minor documentation issue. The feature is quite usable now so it gets formally documented and enabled. There is no behavior change for people not using the `SRC` or `ALLSRC` in rebase destination revset. .. feature:: Rebase with different destination per source revision Previously, rebase only supports one unique destination. Now ``SRC`` and ``ALLSRC`` can be used in rebase destination revset to precisely define destination per each individual source revision. For example, the following command could move some orphaned changesets to reasonable new places so they become no longer orphaned:: hg rebase -r 'orphan()-obsolete()' -d 'max((successors(max(roots(ALLSRC) & ::SRC)^)-obsolete())::)' Differential Revision: https://phab.mercurial-scm.org/D1063

overlayworkingctx: make clean() public It will be called directly by rebase after concluding a node. Differential Revision: https://phab.mercurial-scm.org/D1230

overlayworkingctx: remove flushall() Differential Revision: https://phab.mercurial-scm.org/D1216

merge: skip subrepo state, update hooks, and updating the dirstate in IMM Differential Revision: https://phab.mercurial-scm.org/D1215

merge: remove calls to flushall() Since D1105, these are unnecessary since IMM will now never use workers. Differential Revision: https://phab.mercurial-scm.org/D1213

filemerge: raise InMemoryMergeConflictsError if we hit merge conflicts in IMM Merge conflicts might be supported in the future, but for now are kept out of scope. Any places where we used to call `flushall()` should be replaced with some kind of exception. At this point, IMM M1 is no longer supported. Differential Revision: https://phab.mercurial-scm.org/D1212