Deprecation warnings will be printed there. auto_tracking_matcher(ui) could
be cached, but there aren't many callers right now, so it should be okay to
parse and emit warnings for each invocation. Other than that, the changes are
straightforward.
We had both `repo()` and `mut_repo()` on `Transaction` and I think it
was easy to get confused and think that the former returned a
`&ReadonlyRepo` but both of them actually return a reference to
`MutableRepo` (the latter obviously returns a mutable reference). I
hope that renaming to the more idiomatic `repo_mut()` will help
clarify.
We could instead have renamed them to `mut_repo()` and
`mut_repo_mut()` but that seemed unnecessarily long. It would better
match the `mut_repo` variables we typically use, though.
The rewritten code is already a no-op when there's a single input. I
don't think the case is common enough to warrant having a special case
for performance reasons either. Also, by not having the special case,
`jj parallelize <immutable commit>` fails consistently with the
non-singleton case.
`jj parallelize` was a good example of a command that can be
simplified by the new API, so I decided to rewrite it as an example.
The rewritten version is more flexible and doesn't actually need the
restrictions from the old version (such as checking that the commits
are connected). I still left the check for now to keep this patch
somewhat small. A subsequent commit will remove the restrictions.
I'm going to add a helper struct to help with rewriting commits. I
want to make that struct own the old commit and the new parents to
simplify lifetimes. This patch prepares for that by passing the
commits by value to `rebase_commit()`.
Parallelize revisions by making them siblings
Running `jj parallelize 1::2` will transform the history like this:
```text
3
| 3
2 / \
| -> 1 2
1 \ /
| 0
0
```
Each of the target revisions is rebased onto the parents of the root(s) of
the target revset (not to be confused with the repo root). The children of
the head(s) of the target revset are rebased onto the target revisions.
The target revset is the union of the REVISIONS arguments.
The target revset being parallelized must satisfy several conditions,
otherwise the command will fail.
1. The heads of the target revset must not have different children.
2. The roots of the target revset must not have different parents.
3. The parents of all target revisions except the roots must also be
parallelized. This means that the target revisions must be connected.
