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