Extend github context with host-workspace (#2517)

* hash files translation works with host context translated

* Change file encoding to utf8 for PipelineTemplateConstants.cs

* infer the feature flag on hash files based on the existence of the context

* encoded utf8 with bom

* rename host-workspace to host-work-directory and feature flag the new context var

* Added comment to explain ignore host work directory resolution

Co-authored-by: fhammerl <fhammerl@github.com>

* trigger pipeline

* Move to the github host-workspace context instead of the runner host-work-directory

* remove unused imports

---------

Co-authored-by: fhammerl <fhammerl@github.com>

src/Runner.Worker/ExecutionContext.cs

@@ -1355,6 +1355,12 @@ namespace GitHub.Runner.Worker
         {
             foreach (var key in dict.Keys.ToList())
             {
+                if (key == PipelineTemplateConstants.HostWorkspace)
+                {
+                    // The HostWorkspace context var is excluded so that there is a var that always points to the host path. 
+                    // This var can be used to translate back from container paths, e.g. in HashFilesFunction, which always runs on the host machine
+                    continue;
+                }
                 if (dict[key] is StringContextData)
                 {
                     var value = dict[key].ToString();

src/Runner.Worker/Expressions/HashFilesFunction.cs

@@ -26,11 +26,18 @@ namespace GitHub.Runner.Worker.Expressions
             ArgUtil.NotNull(githubContextData, nameof(githubContextData));
             var githubContext = githubContextData as DictionaryContextData;
             ArgUtil.NotNull(githubContext, nameof(githubContext));
-            githubContext.TryGetValue(PipelineTemplateConstants.Workspace, out var workspace);
+
+            if (!githubContext.TryGetValue(PipelineTemplateConstants.HostWorkspace, out var workspace))
+            {
+                githubContext.TryGetValue(PipelineTemplateConstants.Workspace, out workspace);
+            }
+            ArgUtil.NotNull(workspace, nameof(workspace));
+
             var workspaceData = workspace as StringContextData;
             ArgUtil.NotNull(workspaceData, nameof(workspaceData));
 
             string githubWorkspace = workspaceData.Value;
+
             bool followSymlink = false;
             List<string> patterns = new();
             var firstParameter = true;

src/Runner.Worker/JobExtension.cs

@@ -175,7 +175,14 @@ namespace GitHub.Runner.Worker
                     context.Debug("Update context data");
                     string _workDirectory = HostContext.GetDirectory(WellKnownDirectory.Work);
                     context.SetRunnerContext("workspace", Path.Combine(_workDirectory, trackingConfig.PipelineDirectory));
-                    context.SetGitHubContext("workspace", Path.Combine(_workDirectory, trackingConfig.WorkspaceDirectory));
+
+                    var githubWorkspace = Path.Combine(_workDirectory, trackingConfig.WorkspaceDirectory);
+                    if (jobContext.Global.Variables.GetBoolean(Constants.Runner.Features.UseContainerPathForTemplate) ?? false)
+                    {
+                        // This value is used to translate paths from the container path back to the host path.
+                        context.SetGitHubContext("host-workspace", githubWorkspace);
+                    }
+                    context.SetGitHubContext("workspace", githubWorkspace);
 
                     // Temporary hack for GHES alpha
                     var configurationStore = HostContext.GetService<IConfigurationStore>();

src/Sdk/DTPipelines/Pipelines/ObjectTemplating/PipelineTemplateConstants.cs

@@ -82,5 +82,6 @@ namespace GitHub.DistributedTask.Pipelines.ObjectTemplating
         public const String WorkflowRoot = "workflow-root";
         public const String WorkingDirectory = "working-directory";
         public const String Workspace = "workspace";
+        public const String HostWorkspace = "host-workspace";
     }
 }