rebase: update commit hash references in the new commits This excludes the --collapse case because degenerating to p1 is almost certainly as wrong as leaving the old hashes in place. I expect most people to amend the message explicitly when using that. Differential Revision: https://phab.mercurial-scm.org/D9229

histedit: drop fallback to empty string from rendertemplate() AFAICT, `cmdutil.rendertemplate()` always returns bytes (never e.g. `None`), so we don't need to fall back to empty (byte-)string. The fallback has been there since the code was added in 11c076786d56 (histedit: add templating support to histedit's rule file generation, 2019-01-29). Differential Revision: https://phab.mercurial-scm.org/D9244

phases: convert registernew users to use revision sets Differential Revision: https://phab.mercurial-scm.org/D9233

phases: allow registration and boundary advancement with revision sets The core internals either use revision sets already or can trivially use them. Use the new interface in cg1unpacker.apply to avoid materializing the list of all new nodes as it is normally just a revision range. This avoids about 67 Bytes / changeset on AMD64 in peak RSS. Differential Revision: https://phab.mercurial-scm.org/D9232