v0.19.0

### Breaking changes

* In revset aliases, top-level `kind:pattern` expression is now parsed as
  modifier. Surround with parentheses if it should be parsed as string/file
  pattern.

* Dropped support for automatic upgrade of repo formats used by versions before
  0.12.0.

* `jj fix` now defaults to the broader revset `-s reachable(@, mutable())`
  instead of `-s @`.

* Dropped support for deprecated `jj branch delete`/`forget` `--glob` option.

* `jj branch set` now creates new branch if it doesn't exist. Use `jj branch
  move` to ensure that the target branch already exists.
  [#3584](https://github.com/martinvonz/jj/issues/3584)

### Deprecations

* Replacing `-l` shorthand for `--limit` with `-n` in `jj log`, `jj op log`
  and `jj obslog`.

* `jj split --siblings` is deprecated in favor of `jj split --parallel` (to
  match `jj parallelize`).

* A new `jj file` subcommand now replaces several existing uncategorized
  commands, which are deprecated.
  - `jj file show` replaces `jj cat`.
  - `jj file chmod` replaces `jj chmod`.
  - `jj file list` replaces `jj files`.

### New features

* Support background filesystem monitoring via watchman triggers enabled with
  the `core.watchman.register_snapshot_trigger = true` config.

* Show paths to config files when configuration errors occur.

* `jj fix` now supports configuring the default revset for `-s` using the
  `revsets.fix` config.

* The `descendants()` revset function now accepts an optional `depth` argument;
  like the `ancestors()` depth argument, it limits the depth of the set.

* Revset/template aliases now support function overloading.
  [#2966](https://github.com/martinvonz/jj/issues/2966)

* Conflicted files are individually simplified before being materialized.

* The `jj file` subcommand now contains several existing file utilities.
  - `jj file show`, replacing `jj cat`.
  - `jj file chmod` replacing `jj chmod`.
  - `jj file list` replacing `jj files`.

* New command `jj branch move` let you update branches by name pattern or source
  revision.

* New diff option `jj diff --name-only` allows for easier shell scripting.

* In color-words diffs, hunks are now highlighted with underline. See [diff
  colors and styles](docs/config.md#diff-colors-and-styles) for customization.

* `jj git push -c <arg>` can now accept revsets that resolve to multiple
  revisions. This means that `jj git push -c xyz -c abc` is now equivalent to
  `jj git push -c 'all:(xyz | abc)'`.

* `jj prev` and `jj next` have gained a `--conflict` flag which moves you
  to the next conflict in a child commit.

* New command `jj git remote set-url` that sets the url of a git remote.

* Author timestamp is now reset when rewriting discardable commits (empty
  commits with no description) if authored by the current user.
  [#2000](https://github.com/martinvonz/jj/issues/2000)

* `jj commit` now accepts `--reset-author` option to match `jj describe`.

* `jj squash` now accepts a `--keep-emptied` option to keep the source commit.

### Fixed bugs

* `jj git push` now ignores immutable commits when checking whether a
  to-be-pushed commit has conflicts, or has no description / committer / author
  set. [#3029](https://github.com/martinvonz/jj/issues/3029)

* `jj` will look for divergent changes outside the short prefix set even if it
  finds the change id inside the short prefix set.
  [#2476](https://github.com/martinvonz/jj/issues/2476)

### Contributors

Thanks to the people who made this release happen!

* Austin Seipp (@thoughtpolice)
* Benjamin Tan (@bnjmnt4n)
* Daniel Ploch (@torquestomp)
* Danny Hooper (@hooper)
* Ilya Grigoriev (@ilyagr)
* James Sully (@sullyj3)
* Jonathan Tan (@jonathantanmy)
* Kyle J Strand (@BatmanAoD)
* Manuel Caldeira (@KiitoX)
* Martin von Zweigbergk (@martinvonz)
* Matt Kulukundis (@fowles)
* Matt Stark (@matts1)
* mlcui (@mlcui-corp)
* Philip Metzger (@PhilipMetzger)
* Scott Taylor (@scott2000)
* Simon Wollwage (@Kintaro)
* Tal Pressman (@tp-woven)
* Yuya Nishihara (@yuja)