add set-workspace command

src/Runner.Common/ExtensionManager.cs

@@ -42,6 +42,7 @@ namespace GitHub.Runner.Common
                 // Action command extensions.
                 case "GitHub.Runner.Worker.IActionCommandExtension":
                     Add<T>(extensions, "GitHub.Runner.Worker.InternalPluginSetRepoPathCommandExtension, Runner.Worker");
+                    Add<T>(extensions, "GitHub.Runner.Worker.SetWorkspaceCommandExtension, Runner.Worker");
                     Add<T>(extensions, "GitHub.Runner.Worker.SetEnvCommandExtension, Runner.Worker");
                     Add<T>(extensions, "GitHub.Runner.Worker.SetOutputCommandExtension, Runner.Worker");
                     Add<T>(extensions, "GitHub.Runner.Worker.SaveStateCommandExtension, Runner.Worker");

src/Runner.Worker/ActionCommandManager.cs

@@ -184,6 +184,40 @@ namespace GitHub.Runner.Worker
         }
     }
 
+    public sealed class SetWorkspaceCommandExtension : RunnerService, IActionCommandExtension
+    {
+        public string Command => "set-workspace";
+
+        public Type ExtensionType => typeof(IActionCommandExtension);
+
+        public void ProcessCommand(IExecutionContext context, string line, ActionCommand command)
+        {
+            string path = command.Data;
+            if (string.IsNullOrWhiteSpace(path))
+            {
+                throw new Exception("Path not specified");
+            }
+
+            if (!Path.IsPathRooted(path))
+            {
+                throw new Exception("Expected a rooted path");
+            }
+
+            string runnerWorkspace = context.GetRunnerContext("workspace");
+            ArgUtil.Directory(runnerWorkspace, nameof(runnerWorkspace));
+
+            // Must be under runner workspace
+            path = Path.GetFullPath(path); // remove relative pathing and normalize slashes
+            if (!path.StartsWith(runnerWorkspace + Path.DirectorySeparatorChar, IOUtil.FilePathStringComparison))
+            {
+                throw new Exception($"Expected path to be under {runnerWorkspace}");
+            }
+
+            Trace.Info($"Setting GitHub workspace to '{path}'");
+            context.SetGitHubContext("workspace", path);
+        }
+    }
+
     public sealed class SetEnvCommandExtension : RunnerService, IActionCommandExtension
     {
         public string Command => "set-env";

src/Runner.Worker/ExecutionContext.cs

@@ -78,6 +78,7 @@ namespace GitHub.Runner.Worker
         void Start(string currentOperation = null);
         TaskResult Complete(TaskResult? result = null, string currentOperation = null, string resultCode = null);
         void SetEnvContext(string name, string value);
+        string GetRunnerContext(string name);
         void SetRunnerContext(string name, string value);
         string GetGitHubContext(string name);
         void SetGitHubContext(string name, string value);
@@ -365,6 +366,13 @@ namespace GitHub.Runner.Worker
             return Result.Value;
         }
 
+        public string GetRunnerContext(string name)
+        {
+            ArgUtil.NotNullOrEmpty(name, nameof(name));
+            var runnerContext = ExpressionValues["runner"] as RunnerContext;
+            return runnerContext[name].AssertString($"runner[{name}]");
+        }
+
         public void SetRunnerContext(string name, string value)
         {
             ArgUtil.NotNullOrEmpty(name, nameof(name));