program: fix computation of app path with single file

When publishing GCM as a 'single file' application, the computed path to
the entry executable is no longer correct.

On .NET Core 3.1, using `Assembly.Location` resolves to the temporary
extracted DLL file path. On .NET 5 `Assembly.Location` always returns the
empty string.

Since .NET 5, published single-file apps no longer use the self-
extraction model, and are real single file with all assemblies and
native libraries statically linked/bundled.

We now use the `Environment.GetCommandLineArgs()` method to get the raw
underlying "argv" arguments, which argv[0] is the absolute file path to
the entry executable.

We also change how we get the application version number to look for the
assembly attribute, rather than extract if from the file on disk.

At app startup, also change the way we trace system information to be
more readable.

Author: mjcheetham

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

@@ -3,6 +3,7 @@
 using System;
 using System.IO;
 using System.Reflection;
+using System.Runtime.InteropServices;
 using Atlassian.Bitbucket;
 using GitHub;
 using Microsoft.AzureRepos;
@@ -36,16 +37,19 @@ public static void Main(string[] args)
 
         private static string GetApplicationPath()
         {
-            Assembly entryAssembly = Assembly.GetExecutingAssembly();
-            if (entryAssembly is null)
-            {
-                throw new InvalidOperationException();
-            }
+            // Assembly::Location always returns an empty string if the application was published as a single file
+#pragma warning disable IL3000
+            bool isSingleFile = string.IsNullOrEmpty(Assembly.GetEntryAssembly()?.Location);
+#pragma warning restore IL3000
 
-            string candidatePath = entryAssembly.Location;
+            // Use "argv[0]" to get the full path to the entry executable - this is consistent across
+            // .NET Framework and .NET >= 5 when published as a single file.
+            string[] args = Environment.GetCommandLineArgs();
+            string candidatePath = args[0];
 
-            // Strip the .dll from assembly name on Mac and Linux
-            if (!PlatformUtils.IsWindows() && Path.HasExtension(candidatePath))
+            // If we have not been published as a single file on .NET 5 then we must strip the ".dll" file extension
+            // to get the default AppHost/SuperHost name.
+            if (!isSingleFile && Path.HasExtension(candidatePath))
             {
                 return Path.ChangeExtension(candidatePath, null);
             }

src/shared/Microsoft.Git.CredentialManager/Application.cs

@@ -76,8 +76,13 @@ protected override async Task<int> RunInternalAsync(string[] args)
                 rootCommand.AddCommand(providerCommand);
             }
 
-            // Trace the current version and program arguments
-            Context.Trace.WriteLine($"{Constants.GetProgramHeader()} '{string.Join(" ", args)}'");
+            // Trace the current version, OS, runtime, and program arguments
+            PlatformInformation info = PlatformUtils.GetPlatformInformation();
+            Context.Trace.WriteLine($"Version: {Constants.GcmVersion}");
+            Context.Trace.WriteLine($"Runtime: {info.ClrVersion}");
+            Context.Trace.WriteLine($"Platform: {info.OperatingSystemType} ({info.CpuArchitecture})");
+            Context.Trace.WriteLine($"AppPath: {_appPath}");
+            Context.Trace.WriteLine($"Arguments: {string.Join(" ", args)}");
 
             try
             {

src/shared/Microsoft.Git.CredentialManager/Constants.cs

@@ -1,6 +1,6 @@
 // Copyright (c) Microsoft Corporation. All rights reserved.
 // Licensed under the MIT license.
-using System.Diagnostics;
+using System;
 using System.Reflection;
 
 namespace Microsoft.Git.CredentialManager
@@ -105,35 +105,35 @@ public static class HelpUrls
             public const string GcmLinuxCredStores     = "https://aka.ms/gcmcore-linuxcredstores";
         }
 
-        private static string _gcmVersion;
+        private static Version _gcmVersion;
 
-        /// <summary>
-        /// The current version of Git Credential Manager.
-        /// </summary>
-        public static string GcmVersion
+        public static Version GcmVersion
         {
             get
             {
                 if (_gcmVersion is null)
                 {
-                    _gcmVersion = FileVersionInfo.GetVersionInfo(Assembly.GetExecutingAssembly().Location).ProductVersion;
+                    var assembly = Assembly.GetEntryAssembly() ?? Assembly.GetExecutingAssembly();
+                    var attr = assembly.GetCustomAttribute<AssemblyFileVersionAttribute>();
+                    if (attr is null)
+                    {
+                        _gcmVersion = assembly.GetName().Version;
+                    }
+                    else if (Version.TryParse(attr.Version, out Version asmVersion))
+                    {
+                        _gcmVersion = asmVersion;
+                    }
+                    else
+                    {
+                        // Unknown version!
+                        _gcmVersion = new Version(0, 0);
+                    }
                 }
 
                 return _gcmVersion;
             }
         }
 
-        /// <summary>
-        /// Get standard program header title for Git Credential Manager, including the current version and OS information.
-        /// </summary>
-        /// <returns>Standard program header.</returns>
-        public static string GetProgramHeader()
-        {
-            PlatformInformation info = PlatformUtils.GetPlatformInformation();
-
-            return $"Git Credential Manager version {GcmVersion} ({info.OperatingSystemType}, {info.ClrVersion})";
-        }
-
         /// <summary>
         /// Get the HTTP user-agent for Git Credential Manager.
         /// </summary>