Refactor dart format (dart-lang#5845)

Fixes dart-lang#4440

---------

Co-authored-by: Marya <[email protected]>

src/content/tools/dart-format.md

@@ -1,73 +1,99 @@
 ---
 title: dart format
 description: Command-line tool for formatting Dart source code.
-toc: false
 ---
 
-Use the `dart format` command to replace the whitespace in your program
-with formatting that follows
-[Dart guidelines](/effective-dart/style#formatting).
-This is the same formatting that you can get
-when using an IDE or editor that has Dart support.
+To update your code to follow the
+[Dart formatting guidelines][dart-guidelines],
+use the `dart format` command.
+This formatting follows what you get
+when using an IDE or editor with Dart support.
 
 {% render 'tools/dart-tool-note.md' %}
 
-Provide a list of files or directories to the `dart format` command.
-For example, here's how to format all the Dart files
-in or under the current directory:
+## Specify files to format
+
+To reformat one or more Dart files,
+provide a list of paths to the desired files or directories.
+
+### Specify one path
+
+Provide the path to one file or directory.
+If you specify a directory, `dart format` affects only the files in the
+immediate directory; it doesn't recurse through subdirectories.
+
+**Example:** To format all the Dart files in or under the current directory:
 
 ```console
 $ dart format .
 ```
 
-To specify multiple files or directories,
-use a space-delimited list.
-The following command formats all Dart files under the `lib` directory,
+### Specify multiple paths
+
+To specify multiple files or directories, use a space-delimited list.
+
+**Example:** To format all Dart files under the `lib` directory,
 plus one Dart file under the `bin` directory:
 
 ```console
 $ dart format lib bin/updater.dart 
 ```
 
-:::warning Notice
+### Prevent overwriting Dart files
+
 By default, `dart format` **overwrites** the Dart files.
-:::
 
-If you don't want to overwrite the files,
-add the `--output` or `-o` flag.
-Use `-o show` or `-o json` to get the contents of the formatted files,
-or `-o none` to see only which files would change.
+* To not overwrite the files, add the `--output` or `-o` flag.
+* To get the contents of the formatted files, add `-o show` or `-o json`.
+* To see only which files _would_ change, add `-o none`.
 
 ```console
 $ dart format -o show bin/my_app.dart
 ```
 
-To make the command have an exit code of `1`
-if any formatting changes occur,
+## Notify when changes occur
+
+To make `dart format` return an exit code when formatting changes occur,
 add the `--set-exit-if-changed` flag.
-This exit code is often used with continuous integration (CI)
-to indicate that a check should fail.
+
+* If changes occur, the `dart format` command returns an exit code of `1`.
+* If changes don't occur, the `dart format` command returns an exit code of `0`.
+
+Use exit codes with continuous integration (CI) systems
+so they can trigger another action in response to the exit code.
 
 ```console
 $ dart format -o none --set-exit-if-changed bin/my_app.dart
 ```
 
-For information on additional command-line options,
-use the `dart help` command or see the documentation for the
-[dart_style package.]({{site.pub-pkg}}/dart_style)
+## Use trailing commas
 
-```console
-$ dart help format
-```
+Use optional trailing commas for better automatic formatting.
+Add a trailing comma at the end of parameter lists in functions, methods,
+and constructors.
+This helps the formatter insert the appropriate amount of line breaks for
+Dart-style code.
+
+## Affects whitespace only
 
-:::tip
 To avoid making changes that might be unsafe,
 `dart format` only affects whitespace.
 
 There's a lot more to writing readable and
 consistent code than just whitespace, though.
 To learn more about best practices for writing and styling Dart code,
 check out the [Dart style guide][].
-:::
+
+## Learn more
+
+To learn about additional command-line options,
+use the `dart help` command or see the documentation for the
+[dart_style package][dart_style]
+
+```console
+$ dart help format
+```
 
 [Dart style guide]: /effective-dart/style
+[dart_style]: {{site.pub-pkg}}/dart_style
+[dart-guidelines]: /effective-dart/style#formatting