Pin formatter to a specific version

pubspec.yaml

 name: dev_compiler
 description: Dart dev checker / compiler
 dependencies:
   analyzer:
     git:
       url: git@github.com:dart-lang/ddc_analyzer.git
       ref: master
   args: ^0.12.1
   cli_util: ^0.0.1
   crypto: ^0.9.0
-  dart_style:
-    git:
-      url: git@github.com:dart-lang/dart_style.git
-      ref: master
+  # We pin a specific version to ensure everyone is formatting the code exactly
+  # the same way. This is because any change in dart_style, even non-braking
+  # changes, may change the output format.
+  dart_style: 0.1.7
   html5lib: ^0.12.0
   logging: ^0.9.2
   path: ^1.3.0
   shelf: ^0.6.0
   shelf_static: ^0.2.1
   source_maps: ^0.10.0
   source_span: ^1.0.0
   stack_trace: ^1.1.1
 dev_dependencies:
   pub_semver: ^1.1.0
   unittest: ^0.11.0
 dependency_overrides:
   analyzer:
     git:
       url: git@github.com:dart-lang/ddc_analyzer.git
       ref: master
 executables:
   # Similar to "analyzer.dart" and its command line "dartanalyzer", we use
   # "dartdevc" and "devc.dart"
   dartdevc: devc