trace2: add child_start and child_exit events

Write the TRACE2 child_start and child_exit events for each child
process invoked by GCM.

src/shared/Core/Authentication/AuthenticationBase.cs

@@ -43,7 +43,7 @@ protected AuthenticationBase(ICommandContext context)
             // authentication helper's messages.
             Context.Trace.Flush();
 
-            var process = ChildProcess.Start(Context.Trace2, procStartInfo);
+            var process = ChildProcess.Start(Context.Trace2, procStartInfo, Trace2ProcessClass.UIHelper);
             if (process is null)
             {
                 throw new Exception($"Failed to start helper process: {path} {args}");

src/shared/Core/ChildProcess.cs

@@ -11,6 +11,7 @@ public class ChildProcess : DisposableObject
 
     private DateTimeOffset _startTime;
     private DateTimeOffset _exitTime => Process.ExitTime;
+    private ProcessStartInfo _startInfo => Process.StartInfo;
 
     private int _id => Process.Id;
 
@@ -19,26 +20,38 @@ public class ChildProcess : DisposableObject
     public StreamWriter StandardInput => Process.StandardInput;
     public StreamReader StandardOutput => Process.StandardOutput;
     public StreamReader StandardError => Process.StandardError;
-    public int Id => Process.Id;
     public int ExitCode => Process.ExitCode;
 
-    public static ChildProcess Start(ITrace2 trace2, ProcessStartInfo startInfo)
+    public static ChildProcess Start(ITrace2 trace2, ProcessStartInfo startInfo, Trace2ProcessClass processClass)
     {
         var childProc = new ChildProcess(trace2, startInfo);
-        childProc.Start();
+        childProc.Start(processClass);
         return childProc;
     }
 
     public ChildProcess(ITrace2 trace2, ProcessStartInfo startInfo)
     {
         _trace2 = trace2;
         Process = new Process() { StartInfo = startInfo };
+        Process.Exited += ProcessOnExited;
     }
 
-    public void Start()
+    public void Start(Trace2ProcessClass processClass)
     {
         ThrowIfDisposed();
+        // Record the time just before the process starts, since:
+        // (1) There is no event related to Start as there is with Exit.
+        // (2) Using Process.StartTime causes a race condition that leads
+        // to an exception if the process finishes executing before the
+        // variable is passed to Trace2.
+        _startTime = DateTimeOffset.UtcNow;
         Process.Start();
+        _trace2.WriteChildStart(
+            _startTime,
+            processClass,
+            _startInfo.UseShellExecute,
+            _startInfo.FileName,
+            _startInfo.Arguments);
     }
 
     public void WaitForExit() => Process.WaitForExit();
@@ -47,7 +60,20 @@ public void Start()
 
     protected override void ReleaseManagedResources()
     {
+        Process.Exited -= ProcessOnExited;
         Process.Dispose();
         base.ReleaseUnmanagedResources();
     }
+
+    private void ProcessOnExited(object sender, EventArgs e)
+    {
+        if (sender is Process)
+        {
+            double elapsedTime = (_exitTime - _startTime).TotalSeconds;
+            _trace2.WriteChildExit(
+                elapsedTime,
+                _id,
+                Process.ExitCode);
+        }
+    }
 }

src/shared/Core/Diagnostics/GitDiagnostic.cs

@@ -25,7 +25,7 @@ protected override Task<bool> RunInternalAsync(StringBuilder log, IList<string>
 
             log.Append("Listing all Git configuration...");
             ChildProcess configProc = CommandContext.Git.CreateProcess("config --list --show-origin");
-            configProc.Start();
+            configProc.Start(Trace2ProcessClass.Git);
             // To avoid deadlocks, always read the output stream first and then wait
             // TODO: don't read in all the data at once; stream it
             string gitConfig = configProc.StandardOutput.ReadToEnd().TrimEnd();

src/shared/Core/Git.cs

@@ -90,7 +90,7 @@ public GitVersion Version
                 {
                     using (var git = CreateProcess("version"))
                     {
-                        git.Start();
+                        git.Start(Trace2ProcessClass.Git);
 
                         string data = git.StandardOutput.ReadToEnd();
                         git.WaitForExit();
@@ -120,7 +120,7 @@ public string GetCurrentRepository()
         {
             using (var git = CreateProcess("rev-parse --absolute-git-dir"))
             {
-                git.Start();
+                git.Start(Trace2ProcessClass.Git);
                 string data = git.StandardOutput.ReadToEnd();
                 git.WaitForExit();
 
@@ -141,7 +141,7 @@ public IEnumerable<GitRemote> GetRemotes()
         {
             using (var git = CreateProcess("remote -v show"))
             {
-                git.Start();
+                git.Start(Trace2ProcessClass.Git);
                 // To avoid deadlocks, always read the output stream first and then wait
                 // TODO: don't read in all the data at once; stream it
                 string data = git.StandardOutput.ReadToEnd();

src/shared/Core/GitConfiguration.cs

@@ -129,7 +129,7 @@ public void Enumerate(GitConfigurationLevel level, GitConfigurationEnumerationCa
             string levelArg = GetLevelFilterArg(level);
             using (ChildProcess git = _git.CreateProcess($"config --null {levelArg} --list"))
             {
-                git.Start();
+                git.Start(Trace2ProcessClass.Git);
                 // To avoid deadlocks, always read the output stream first and then wait
                 // TODO: don't read in all the data at once; stream it
                 string data = git.StandardOutput.ReadToEnd();
@@ -198,7 +198,7 @@ public bool TryGet(GitConfigurationLevel level, GitConfigurationType type, strin
             string typeArg = GetCanonicalizeTypeArg(type);
             using (ChildProcess git = _git.CreateProcess($"config --null {levelArg} {typeArg} {QuoteCmdArg(name)}"))
             {
-                git.Start();
+                git.Start(Trace2ProcessClass.Git);
                 // To avoid deadlocks, always read the output stream first and then wait
                 // TODO: don't read in all the data at once; stream it
                 string data = git.StandardOutput.ReadToEnd();
@@ -236,7 +236,7 @@ public void Set(GitConfigurationLevel level, string name, string value)
             string levelArg = GetLevelFilterArg(level);
             using (ChildProcess git = _git.CreateProcess($"config {levelArg} {QuoteCmdArg(name)} {QuoteCmdArg(value)}"))
             {
-                git.Start();
+                git.Start(Trace2ProcessClass.Git);
                 git.WaitForExit();
 
                 switch (git.ExitCode)
@@ -257,7 +257,7 @@ public void Add(GitConfigurationLevel level, string name, string value)
             string levelArg = GetLevelFilterArg(level);
             using (ChildProcess git = _git.CreateProcess($"config {levelArg} --add {QuoteCmdArg(name)} {QuoteCmdArg(value)}"))
             {
-                git.Start();
+                git.Start(Trace2ProcessClass.Git);
                 git.WaitForExit();
 
                 switch (git.ExitCode)
@@ -278,7 +278,7 @@ public void Unset(GitConfigurationLevel level, string name)
             string levelArg = GetLevelFilterArg(level);
             using (ChildProcess git = _git.CreateProcess($"config {levelArg} --unset {QuoteCmdArg(name)}"))
             {
-                git.Start();
+                git.Start(Trace2ProcessClass.Git);
                 git.WaitForExit();
 
                 switch (git.ExitCode)
@@ -302,7 +302,7 @@ public IEnumerable<string> GetAll(GitConfigurationLevel level, GitConfigurationT
 
             using (ChildProcess git = _git.CreateProcess(gitArgs))
             {
-                git.Start();
+                git.Start(Trace2ProcessClass.Git);
                 // To avoid deadlocks, always read the output stream first and then wait
                 // TODO: don't read in all the data at once; stream it
                 string data = git.StandardOutput.ReadToEnd();
@@ -344,7 +344,7 @@ public IEnumerable<string> GetRegex(GitConfigurationLevel level, GitConfiguratio
 
             using (ChildProcess git = _git.CreateProcess(gitArgs))
             {
-                git.Start();
+                git.Start(Trace2ProcessClass.Git);
                 // To avoid deadlocks, always read the output stream first and then wait
                 // TODO: don't read in all the data at once; stream it
                 string data = git.StandardOutput.ReadToEnd();
@@ -386,7 +386,7 @@ public void ReplaceAll(GitConfigurationLevel level, string name, string valueReg
 
             using (ChildProcess git = _git.CreateProcess(gitArgs))
             {
-                git.Start();
+                git.Start(Trace2ProcessClass.Git);
                 git.WaitForExit();
 
                 switch (git.ExitCode)
@@ -413,7 +413,7 @@ public void UnsetAll(GitConfigurationLevel level, string name, string valueRegex
 
             using (ChildProcess git = _git.CreateProcess(gitArgs))
             {
-                git.Start();
+                git.Start(Trace2ProcessClass.Git);
                 git.WaitForExit();
 
                 switch (git.ExitCode)

src/shared/Core/PlatformUtils.cs

@@ -338,7 +338,7 @@ private static string GetOSVersion(ITrace2 trace2)
 
                 using (var swvers = new ChildProcess(trace2, psi))
                 {
-                    swvers.Start();
+                    swvers.Start(Trace2ProcessClass.Other);
                     swvers.WaitForExit();
 
                     if (swvers.ExitCode == 0)
@@ -359,7 +359,7 @@ private static string GetOSVersion(ITrace2 trace2)
 
                 using (var uname = new ChildProcess(trace2, psi))
                 {
-                    uname.Start();
+                    uname.Start(Trace2ProcessClass.Other);
                     uname.Process.WaitForExit();
 
                     if (uname.ExitCode == 0)