## Feature Description
If enabled in the user or repository settings, the local branches pointing to the
parents of the revision targeted by `jj commit` will be advanced to the newly
created commit. Support for `jj new` will be added in a future change.
This behavior can be enabled by default for all branches by setting
the following in the config.toml:
```
[experimental-advance-branches]
enabled-branches = ["glob:*"]
```
Specific branches can also be disabled:
```
[experimental-advance-branches]
enabled-branches = ["glob:*"]
disabled-branches = ["main"]
```
Branches that match a disabled pattern will not be advanced, even if they also
match an enabled pattern.
This implements feature request #2338.
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.
this greatly speeds up the time to run all tests, at the cost of slightly larger recompile times for individual tests.
this unfortunately adds the requirement that all tests are listed in `runner.rs` for the crate.
to avoid forgetting, i've added a new test that ensures the directory is in sync with the file.
## benchmarks
before this change, recompiling all tests took 32-50 seconds and running a single test took 3.5 seconds:
```
; hyperfine 'touch lib/src/lib.rs && cargo t --test test_working_copy'
Time (mean ± σ): 3.543 s ± 0.168 s [User: 2.597 s, System: 1.262 s]
Range (min … max): 3.400 s … 3.847 s 10 runs
```
after this change, recompiling all tests take 4 seconds:
```
; hyperfine 'touch lib/src/lib.rs ; cargo t --test runner --no-run'
Time (mean ± σ): 4.055 s ± 0.123 s [User: 3.591 s, System: 1.593 s]
Range (min … max): 3.804 s … 4.159 s 10 runs
```
and running a single test takes about the same:
```
; hyperfine 'touch lib/src/lib.rs && cargo t --test runner -- test_working_copy'
Time (mean ± σ): 4.129 s ± 0.120 s [User: 3.636 s, System: 1.593 s]
Range (min … max): 3.933 s … 4.346 s 10 runs
```
about 1.4 seconds of that is the time for the runner, of which .4 is the time for the linker. so
there may be room for further improving the times.
