Add more debug output to snippet git failures (#83806)

dev/snippets/lib/main.dart

@@ -23,9 +23,12 @@ const String _kShowDartPad = 'dartpad';
 
 String getChannelName() {
   final RegExp gitBranchRegexp = RegExp(r'^## (?<branch>.*)');
-  final ProcessResult gitResult = Process.runSync('git', <String>['status', '-b', '--porcelain']);
+  final ProcessResult gitResult = Process.runSync('git', <String>['status', '-b', '--porcelain'], environment: <String, String>{
+    'GIT_TRACE': '2',
+    'GIT_TRACE_SETUP': '2',
+  }, includeParentEnvironment: true);
   if (gitResult.exitCode != 0)
-    throw 'git status exit with non-zero exit code: ${gitResult.exitCode}';
+    throw 'git status exit with non-zero exit code: ${gitResult.exitCode}: ${gitResult.stderr}';
   final RegExpMatch? gitBranchMatch = gitBranchRegexp.firstMatch(
       (gitResult.stdout as String).trim().split('\n').first);
   return gitBranchMatch == null ? '<unknown>' : gitBranchMatch.namedGroup('branch')!.split('...').first;