Use a shared var to save the value for git existence (dotnet#2090)

src/Microsoft.DocAsCode.Common/Git/GitUtility.cs

@@ -2,30 +2,29 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 namespace Microsoft.DocAsCode.Common.Git
-{
+{
     using System;
     using System.Collections.Concurrent;
     using System.Diagnostics;
     using System.IO;
     using System.Text;
 
+    using Microsoft.DocAsCode.Plugins;
+
     public static class GitUtility
     {
         private static readonly string CommandName = "git";
         private static readonly int GitTimeOut = 1000;
-        private static readonly Lazy<bool> _existGitCommand =
-            new Lazy<bool>(() => CommandUtility.ExistCommand(CommandName));
 
         private static readonly string GetRepoRootCommand = "rev-parse --show-toplevel";
         private static readonly string GetLocalBranchCommand = "rev-parse --abbrev-ref HEAD";
         private static readonly string GetLocalBranchCommitIdCommand = "rev-parse HEAD";
         private static readonly string GetRemoteBranchCommand = "rev-parse --abbrev-ref @{u}";
         private static readonly string GetDeletedFileContentCommand = "show {0}^:{1}";
         private static readonly string GetFileLastCommitIdCommand = "rev-list --max-count=1 --all -- {0}";
+
         // TODO: only get default remote's url currently.
         private static readonly string GetOriginUrlCommand = "config --get remote.origin.url";
-        private static readonly string GetLocalHeadIdCommand = "rev-parse HEAD";
-        private static readonly string GetRemoteHeadIdCommand = "rev-parse @{u}";
 
         private static readonly string[] BuildSystemBranchName = new[]
         {
@@ -39,6 +38,9 @@ public static class GitUtility
 
         private static readonly ConcurrentDictionary<string, GitRepoInfo> Cache = new ConcurrentDictionary<string, GitRepoInfo>();
 
+        private static bool? GitCommandExists = null;
+        private static object SyncRoot = new object();
+
         public static GitDetail TryGetFileDetail(string filePath)
         {
             GitDetail detail = null;
@@ -55,45 +57,15 @@ public static GitDetail TryGetFileDetail(string filePath)
 
         public static GitDetail GetFileDetail(string filePath)
         {
-            if (string.IsNullOrEmpty(filePath))
+            if (string.IsNullOrEmpty(filePath) || !ExistGitCommand())
             {
                 return null;
             }
 
-            if (!Path.IsPathRooted(filePath))
-            {
-                throw new GitException($"{nameof(filePath)} should be an absolute path");
-            }
+            var path = Path.Combine(EnvironmentContext.BaseDirectory, filePath).ToNormalizedPath();
 
-            if (!ExistGitCommand())
-            {
-                throw new GitException("Can't find git command in current environment");
-            }
-
-            filePath = PathUtility.NormalizePath(filePath);
-            var detail = GetFileDetailCore(filePath);
+            var detail = GetFileDetailCore(path);
             return detail;
-        }
-
-        public static string GetDeletedFileContent(string filePath)
-        {
-            if (string.IsNullOrEmpty(filePath))
-            {
-                return null;
-            }
-
-            if (!Path.IsPathRooted(filePath))
-            {
-                throw new GitException($"{nameof(filePath)} should be an absolute path");
-            }
-
-            if (!ExistGitCommand())
-            {
-                throw new GitException("Can't find git command in current environment");
-            }
-
-            filePath = PathUtility.NormalizePath(filePath);
-            return GetDeletedFileContentCore(filePath);
         }
 
         public static GitRepoInfo GetRepoInfo(string directory)
@@ -118,36 +90,6 @@ public static GitRepoInfo GetRepoInfo(string directory)
         }
 
         #region Private Methods
-        private static string GetDeletedFileContentCore(string filePath)
-        {
-            string directory;
-            if (PathUtility.IsDirectory(filePath))
-            {
-                directory = filePath;
-            }
-            else
-            {
-                directory = Path.GetDirectoryName(filePath);
-            }
-
-            var repoInfo = Cache.GetOrAdd(directory, GetRepoInfo);
-
-            if (repoInfo == null)
-            {
-                return null;
-            }
-
-            var getFileLastCommitIdCommand = string.Format(GetFileLastCommitIdCommand, PathUtility.MakeRelativePath(repoInfo.RepoRootPath, filePath));
-            var lastCommitId = TryRunGitCommandAndGetLastLine(repoInfo.RepoRootPath, getFileLastCommitIdCommand);
-
-            if (lastCommitId == null)
-            {
-                return null;
-            }
-
-            var getDeletedFileContentCommand = string.Format(GetDeletedFileContentCommand, lastCommitId, PathUtility.MakeRelativePath(repoInfo.RepoRootPath, filePath));
-            return TryRunGitCommand(repoInfo.RepoRootPath, getDeletedFileContentCommand);
-        }
 
         private static bool IsGitRoot(string directory)
         {
@@ -356,8 +298,19 @@ private static void RunGitCommand(string repoPath, string arguments, Action<stri
 
         private static bool ExistGitCommand()
         {
-            return _existGitCommand.Value;
+            if (GitCommandExists == null)
+            {
+                lock (SyncRoot)
+                {
+                    if (GitCommandExists == null)
+                    {
+                        GitCommandExists = CommandUtility.ExistCommand(CommandName);
+                    }
+                }
+            }
+            return GitCommandExists.Value;
         }
+
         #endregion
     }
 }

test/Microsoft.DocAsCode.Common.Tests/GitUtilityTest.cs

@@ -33,19 +33,5 @@ public void Environment_ForBranchName()
             var info = GitUtility.GetFileDetail(Directory.GetCurrentDirectory());
             Assert.Equal("special-branch", info.RemoteBranch);
         }
-
-        [Fact]
-        public void GetDeletedFile()
-        {
-            var repoInfo = GitUtility.GetRepoInfo(Directory.GetCurrentDirectory());
-            var deletedExistingFile = Path.Combine(repoInfo.RepoRootPath, @"src/docfx.website.themes/angular/README.md");
-            var deletedNotExistingFile = Path.Combine(repoInfo.RepoRootPath, @"NOTEXISTING.md");
-
-            var content = GitUtility.GetDeletedFileContent(deletedExistingFile);
-            Assert.NotNull(content);
-
-            content = GitUtility.GetDeletedFileContent(deletedNotExistingFile);
-            Assert.Null(content);
-        }
     }
 }