trace2: add process depth calculation

The performance format target requires recording of process depth. We use
the number of forward slashes in the process's sid as a convenient way to
determine this. Because the sid and the depth are process-related
concepts, this change also moves sid/depth related properties into
ProcessManager.cs and removes the SidManager.cs class.

Author: ldennington

src/shared/Atlassian.Bitbucket.UI.Avalonia/Program.cs

@@ -47,7 +47,7 @@ private static void AppMain(object o)
 
             // Set the session id (sid) for the helper process, to be
             // used when TRACE2 tracing is enabled.
-            SidManager.CreateSid();
+            ProcessManager.CreateSid();
             using (var context = new CommandContext())
             using (var app = new HelperApplication(context))
             {

src/shared/Core.Tests/ProcessManagerTests.cs

@@ -0,0 +1,20 @@
+using GitCredentialManager;
+using Xunit;
+
+namespace Core.Tests;
+
+public class ProcessManagerTests
+{
+    [Theory]
+    [InlineData("", 0)]
+    [InlineData("foo", 0)]
+    [InlineData("foo/bar", 1)]
+    [InlineData("foo/bar/baz", 2)]
+    public void TryGetProcessDepth_Returns_Expected_Depth(string input, int expected)
+    {
+        ProcessManager.Sid = input;
+        var actual = ProcessManager.GetProcessDepth();
+
+        Assert.Equal(expected, actual);
+    }
+}

src/shared/Core/ProcessManager.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Diagnostics;
 using System.Threading.Tasks;
 
@@ -27,8 +28,14 @@ public interface IProcessManager
 
 public class ProcessManager : IProcessManager
 {
+    private const string SidEnvar = "GIT_TRACE2_PARENT_SID";
+
     private readonly ITrace2 _trace2;
 
+    public static string Sid { get; internal set; }
+
+    public static int Depth { get; internal set; }
+
     public ProcessManager(ITrace2 trace2)
     {
         _trace2 = trace2;
@@ -48,9 +55,52 @@ public virtual ChildProcess CreateProcess(string path, string args, bool useShel
         return CreateProcess(psi);
     }
 
-
     public virtual ChildProcess CreateProcess(ProcessStartInfo psi)
     {
         return new ChildProcess(_trace2, psi);
     }
+
+    /// <summary>
+    /// Create a TRACE2 "session id" (sid) for this process.
+    /// </summary>
+    public static void CreateSid()
+    {
+        Sid = Environment.GetEnvironmentVariable(SidEnvar);
+
+        if (!string.IsNullOrEmpty(Sid))
+        {
+            Sid = $"{Sid}/{Guid.NewGuid():D}";
+        }
+        else
+        {
+            // We are the root process; create our own 'root' SID
+            Sid = Guid.NewGuid().ToString("D");
+        }
+
+        Environment.SetEnvironmentVariable(SidEnvar, Sid);
+        Depth = GetProcessDepth();
+    }
+
+    /// <summary>
+    /// Get "depth" of current process relative to top-level GCM process.
+    /// </summary>
+    /// <returns>Depth of current process.</returns>
+    internal static int GetProcessDepth()
+    {
+        char processSeparator = '/';
+        if (!Sid.Contains(processSeparator))
+        {
+            return 0;
+        }
+
+        int count = 0;
+        // Use AsSpan() for slight performance bump over traditional foreach loop.
+        foreach (var c in Sid.AsSpan())
+        {
+            if (c == processSeparator)
+                count++;
+        }
+
+        return count;
+    }
 }

src/shared/Core/SidManager.cs

@@ -146,7 +146,7 @@ public void Initialize(DateTimeOffset startTime)
 
         _applicationStartTime = startTime;
         _settings = _commandContext.Settings.GetTrace2Settings();
-        _sid = SidManager.Sid;
+        _sid = ProcessManager.Sid;
 
         InitializeWriters();
 

src/shared/Core/Trace2.cs

@@ -45,7 +45,7 @@ private static void AppMain(object o)
 
             // Set the session id (sid) for the helper process, to be
             // used when TRACE2 tracing is enabled.
-            SidManager.CreateSid();
+            ProcessManager.CreateSid();
             using (var context = new CommandContext())
             using (var app = new HelperApplication(context))
             {

src/shared/Git-Credential-Manager.UI.Avalonia/Program.cs

@@ -14,7 +14,7 @@ public static void Main(string[] args)
             var startTime = DateTimeOffset.UtcNow;
             // Set the session id (sid) and start time for the GCM process, to be
             // used when TRACE2 tracing is enabled.
-            SidManager.CreateSid();
+            ProcessManager.CreateSid();
 
             using (var context = new CommandContext())
             using (var app = new Application(context))

src/shared/Git-Credential-Manager/Program.cs

@@ -47,7 +47,7 @@ private static void AppMain(object o)
 
             // Set the session id (sid) for the helper process, to be
             // used when TRACE2 tracing is enabled.
-            SidManager.CreateSid();
+            ProcessManager.CreateSid();
             using (var context = new CommandContext())
             using (var app = new HelperApplication(context))
             {

src/shared/GitHub.UI.Avalonia/Program.cs

@@ -47,7 +47,7 @@ private static void AppMain(object o)
 
             // Set the session id (sid) for the helper process, to be
             // used when TRACE2 tracing is enabled.
-            SidManager.CreateSid();
+            ProcessManager.CreateSid();
             using (var context = new CommandContext())
             using (var app = new HelperApplication(context))
             {

src/shared/GitLab.UI.Avalonia/Program.cs

@@ -14,7 +14,7 @@ public static async Task Main(string[] args)
         {
             // Set the session id (sid) for the helper process, to be
             // used when TRACE2 tracing is enabled.
-            SidManager.CreateSid();
+            ProcessManager.CreateSid();
             using (var context = new CommandContext())
             using (var app = new HelperApplication(context))
             {