provide gitea prefixes via FeatureFlag (#562)

* system.runner.server.github_prefixes
  comma separated list of context names

Author: ChristopherHX

src/Runner.Worker/ExecutionContext.cs

@@ -865,7 +865,7 @@ public void InitializeJob(Pipelines.AgentJobRequestMessage message, Cancellation
             var base64EncodedToken = Convert.ToBase64String(Encoding.UTF8.GetBytes($"x-access-token:{githubAccessToken}"));
             HostContext.SecretMasker.AddValue(base64EncodedToken);
             var githubJob = Global.Variables.Get("system.github.job");
-            var githubContext = new GitHubContext();
+            var githubContext = new GitHubContext(Global.Variables.Get("system.runner.server.github_prefixes")?.Split(","));
             githubContext["token"] = githubAccessToken;
             if (!string.IsNullOrEmpty(githubJob))
             {
@@ -876,8 +876,10 @@ public void InitializeJob(Pipelines.AgentJobRequestMessage message, Cancellation
             {
                 githubContext[pair.Key] = pair.Value;
             }
-            ExpressionValues["github"] = githubContext;
-
+            foreach (var prefix in githubContext.Prefixes)
+            {
+                ExpressionValues[prefix] = githubContext;
+            }
             // Prepend Path
             Global.PrependPath = new List<string>();
 

src/Runner.Worker/GitHubContext.cs

@@ -6,6 +6,10 @@ namespace GitHub.Runner.Worker
 {
     public sealed class GitHubContext : DictionaryContextData, IEnvironmentContextData
     {
+        public GitHubContext(string[] prefixes = null) {
+            Prefixes = prefixes ?? ["github"];
+        }
+
         private readonly HashSet<string> _contextEnvAllowlist = new(StringComparer.OrdinalIgnoreCase)
         {
             "action_path",
@@ -47,27 +51,32 @@ public sealed class GitHubContext : DictionaryContextData, IEnvironmentContextDa
             "workspace"
         };
 
+        public string[] Prefixes { get; }
+
         public IEnumerable<KeyValuePair<string, string>> GetRuntimeEnvironmentVariables()
         {
             foreach (var data in this)
             {
                 if (_contextEnvAllowlist.Contains(data.Key))
                 {
-                    if (data.Value is StringContextData value)
-                    {
-                        yield return new KeyValuePair<string, string>($"GITHUB_{data.Key.ToUpperInvariant()}", value);
-                    }
-                    else if (data.Value is BooleanContextData booleanValue)
+                    foreach (var prefix in Prefixes)
                     {
-                        yield return new KeyValuePair<string, string>($"GITHUB_{data.Key.ToUpperInvariant()}", booleanValue.ToString());
+                        if (data.Value is StringContextData value)
+                        {
+                            yield return new KeyValuePair<string, string>($"{prefix.ToUpperInvariant()}_{data.Key.ToUpperInvariant()}", value);
+                        }
+                        else if (data.Value is BooleanContextData booleanValue)
+                        {
+                            yield return new KeyValuePair<string, string>($"{prefix.ToUpperInvariant()}_{data.Key.ToUpperInvariant()}", booleanValue.ToString());
+                        }
                     }
                 }
             }
         }
 
         public GitHubContext ShallowCopy()
         {
-            var copy = new GitHubContext();
+            var copy = new GitHubContext(Prefixes);
 
             foreach (var pair in this)
             {

src/Runner.Worker/Handlers/CompositeActionHandler.cs

@@ -154,7 +154,10 @@ public async Task RunAsync(ActionRunStage stage)
                     var gitHubContext = step.ExecutionContext.ExpressionValues["github"] as GitHubContext;
                     ArgUtil.NotNull(gitHubContext, nameof(gitHubContext));
                     gitHubContext = gitHubContext.ShallowCopy();
-                    step.ExecutionContext.ExpressionValues["github"] = gitHubContext;
+                    foreach (var prefix in gitHubContext.Prefixes)
+                    {
+                        step.ExecutionContext.ExpressionValues[prefix] = gitHubContext;
+                    }
 
                     // Set GITHUB_ACTION_PATH
                     step.ExecutionContext.SetGitHubContext("action_path", ActionDirectory);