Simplify the version string for customer consumption. (#23578)

Fixes #21825

packages/flutter_tools/lib/src/cache.dart

@@ -112,7 +112,18 @@ class Cache {
 
   String _dartSdkVersion;
 
-  String get dartSdkVersion => _dartSdkVersion ??= platform.version;
+  String get dartSdkVersion {
+    if (_dartSdkVersion == null) {
+      // Make the version string more customer-friendly.
+      // Changes '2.1.0-dev.8.0.flutter-4312ae32' to '2.1.0 (build 2.1.0-dev.8.0 4312ae32)'
+      final String justVersion = platform.version.split(' ')[0];
+      _dartSdkVersion = justVersion.replaceFirstMapped(RegExp(r'(\d+\.\d+\.\d+)(.+)'), (Match match) {
+        final String noFlutter = match[2].replaceAll('.flutter-', ' ');
+        return '${match[1]} (build ${match[1]}$noFlutter)';
+      });
+    }
+    return _dartSdkVersion;
+  }
 
   String _engineRevision;
 

packages/flutter_tools/lib/src/version.dart

@@ -82,7 +82,7 @@ class FlutterVersion {
 
   String get frameworkDate => frameworkCommitDate;
 
-  String get dartSdkVersion => Cache.instance.dartSdkVersion.split(' ')[0];
+  String get dartSdkVersion => Cache.instance.dartSdkVersion;
 
   String get engineRevision => Cache.instance.engineRevision;
   String get engineRevisionShort => _shortGitRevision(engineRevision);
@@ -99,10 +99,10 @@ class FlutterVersion {
     final String engineText = 'Engine • revision $engineRevisionShort';
     final String toolsText = 'Tools • Dart $dartSdkVersion';
 
-    // Flutter 1.3.922-pre.2 • channel master • https://github.com/flutter/flutter.git
-    // Framework • revision 2259c59be8 • 19 minutes ago • 2016-08-15 22:51:40
-    // Engine • revision fe509b0d96
-    // Tools • Dart 1.19.0-dev.5.0
+    // Flutter 1.10.2-pre.69 • channel master • https://github.com/flutter/flutter.git
+    // Framework • revision 340c158f32 (84 minutes ago) • 2018-10-26 11:27:22 -0400
+    // Engine • revision 9c46333e14
+    // Tools • Dart 2.1.0 (build 2.1.0-dev.8.0 bf26f760b1)
 
     return '$flutterText\n$frameworkText\n$engineText\n$toolsText';
   }