Issue 573 Write the results of GET command calls to the log

Use the WriteDictionarySecrets() method to safely log the dictionary of data that will be written back to the calling Git process

When it is necessary to follow the processing in GCM during a call from Git the GCM_TRACE environment variable can be used to print trace information to standard error, however the ultimate output of GET commands would not be included in this trace information

This lack of visibility is especially problematic during multi-stage authentication such as OAuth, adding safe logging of the final output makes it possible to follow the GCM process in realtime from inputs to outputs during Git GET requests

Author: mminns

src/shared/Core/Commands/GetCommand.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Generic;
 using System.Threading.Tasks;
 
@@ -35,6 +36,9 @@ protected override async Task ExecuteInternalAsync(InputArguments input, IHostPr
             output["username"] = credential.Account;
             output["password"] = credential.Password;
 
+            Context.Trace.WriteLine("Writing credentials to output:");
+            Context.Trace.WriteDictionarySecrets(output, new []{ "password" }, StringComparer.OrdinalIgnoreCase);
+
             // Write the values to standard out
             Context.Streams.Out.WriteDictionary(output);
         }