The flutter format ... sub-command is essentially just a wrapper around a dart format ... sub-process call: https://github.com/flutter/flutter/blob/master/packages/flutter_tools/lib/src/commands/format.dart#L36. However, it still has bugs: #109553 which are non-trivial to work around. We should deprecate this flutter format, with a message directing users to migrate to directly using dart format.

Deprecation plan:

• on Flutter's main branch, land a PR to add a deprecation warning to the flutter format sub-command, warning users that it will be removed in a future Flutter release and that all uses of it should be replaced by dart format with the same command line arguments
• once the code from the previous step reaches a stable release, a new change can be made to main that fails with a non-zero exit code, again with directions to start using dart format. This will catch users who either did not see the deprecation warning or chose to ignore it.
• once the code from the previous step reaches a stable release, the command can be deleted from main.

If at any point it is found that customers have a legitimate use of flutter format that cannot be trivially met by substituting dart format for flutter format, we can discuss reverting the change and restoring flutter format.