procutil: distribute code for stdout It makes sense to have the distinction between Python 2 and 3 at the top level, as we have to fight a different kind of battle on each: On Python 3, we get consistent behavior on all platforms, but need to create correctly-behaving binary streams. On Python 2, we have to account for platform differences.

convert: use bytes for value in extra dict The keys and values of the extra dict are expected to be bytes. Before this fix, there was a crash in mercurial.changelog.encodeextra().

overlayworkingctx: remove unused `nofilechanges()` and `_compact()` methods Differential Revision: https://phab.mercurial-scm.org/D8733

rebase: correctly check for empty commit in in-memory mode The new code has a small overhead in the empty commit case, as a `memctx` object is always created, but I don’t think it’s justified here to duplicate code to optimize a relatively unlikely code path. Differential Revision: https://phab.mercurial-scm.org/D8732

memctx: make `parents()` return list of one element if it’s not a merge It is part of the contract of `parents()` that non-merges return a list of one element. `self._parents` is always a list of two elements in `memctx`. Differential Revision: https://phab.mercurial-scm.org/D8731

commit: factor out empty commit check to `basectx.isempty()` This enables reuse in other places, e.g. those dealing with `memctx`. Differential Revision: https://phab.mercurial-scm.org/D8729

overlayworkingctx: rename misleadingly named `isempty()` method This method is only about whether there are file changes, not about whether the commit will be empty or not. One user of the method was incorrectly assuming the latter meaning, leading to the bug for which a test case was added in D8727. I’ve added a FIXME to the code. The original motivation for the rename was that I want to add `committablectx.isempty()`, that properly checks if a commit will be empty, using the exact same logic as in `repo.commit()`, and I wanted to avoid a name clash. Differential Revision: https://phab.mercurial-scm.org/D8728

rebase: add test case that shows that inmemory rebase does not preserve merges Differential Revision: https://phab.mercurial-scm.org/D8727

rebase: remove now unnecessary logic to allow empty commit when branch changes This was a workaround for a bug in the empty commit check in repo.commit(), where the parent branch name was incorrectly compared with the wdir branch name instead of the branch name passed via `extra`. The bug was fixed in D8724. The workaround was introduced in b2415e94b2f5. Differential Revision: https://phab.mercurial-scm.org/D8725

commit: check branch change on to-be-committed changeset This makes a difference when a branch name is passed via the `extra` argument, which will be used as the branch name for the created changeset. The empty commit check should use that branch name instead of whatever was set on the working directory. Besides fixing the bug for which a test case was extended, it enables to remove a workaround in the rebase extension, which will be done in a follow-up patch (D8725). Differential Revision: https://phab.mercurial-scm.org/D8724