Fixing UnityYamlMerge to use merge driver

src/GitHub.Api/Application/ApplicationManagerBase.cs

@@ -190,7 +190,7 @@ public void SetupGit(GitInstaller.GitInstallationState state)
             {
                 if (Environment.RepositoryPath.IsInitialized)
                 {
-                    ConfigureMergeSettings();
+                    UpdateMergeSettings();
 
                     GitClient.LfsInstall()
                         .Catch(e =>
@@ -280,25 +280,58 @@ public void InitializeRepository()
             thread.Start();
         }
 
-        private void ConfigureMergeSettings()
+        private void ConfigureMergeSettings(string keyName = null)
         {
             var unityYamlMergeExec =
                 Environment.UnityApplicationContents.Combine("Tools", "UnityYAMLMerge" + Environment.ExecutableExtension);
-            var yamlMergeCommand = Environment.IsWindows
-                ? $@"'{unityYamlMergeExec}' merge -p ""$BASE"" ""$REMOTE"" ""$LOCAL"" ""$MERGED"""
-                : $@"'{unityYamlMergeExec}' merge -p '$BASE' '$REMOTE' '$LOCAL' '$MERGED'";
 
-            GitClient.SetConfig("merge.unityyamlmerge.cmd", yamlMergeCommand, GitConfigSource.Local).Catch(e => {
-                Logger.Error(e, "Error setting merge.unityyamlmerge.cmd");
+            var yamlMergeCommand = $"'{unityYamlMergeExec}' merge -h -p --force %O %B %A %A";
+
+            keyName = keyName ?? "unityyamlmerge";
+
+            GitClient.SetConfig($"merge.{keyName}.name", "Unity SmartMerge (UnityYamlMerge)", GitConfigSource.Local).Catch(e => {
+                Logger.Error(e, "Error setting merge." + keyName + ".name");
+                return true;
+            }).RunSynchronously();
+
+            GitClient.SetConfig($"merge.{keyName}.driver", yamlMergeCommand, GitConfigSource.Local).Catch(e => {
+                Logger.Error(e, "Error setting merge." + keyName + ".driver");
                 return true;
             }).RunSynchronously();
 
-            GitClient.SetConfig("merge.unityyamlmerge.trustExitCode", "false", GitConfigSource.Local).Catch(e => {
-                Logger.Error(e, "Error setting merge.unityyamlmerge.trustExitCode");
+            GitClient.SetConfig($"merge.{keyName}.recursive", "binary", GitConfigSource.Local).Catch(e => {
+                Logger.Error(e, "Error setting merge." + keyName + ".recursive");
                 return true;
             }).RunSynchronously();
         }
 
+        private void UpdateMergeSettings()
+        {
+            var gitAttributesPath = Environment.RepositoryPath.Combine(".gitattributes");
+            if (gitAttributesPath.FileExists())
+            {
+                var readAllText = gitAttributesPath.ReadAllText();
+                var containsLegacyUnityYamlMergeError = readAllText.Contains("unityamlmerge");
+
+                if (containsLegacyUnityYamlMergeError)
+                {
+                    ConfigureMergeSettings("unityamlmerge");
+                }
+            }
+
+            GitClient.UnSetConfig("merge.unityyamlmerge.cmd", GitConfigSource.Local).Catch(e => {
+                Logger.Error(e, "Error removing merge.unityyamlmerge.cmd");
+                return true;
+            }).RunSynchronously();
+
+            GitClient.UnSetConfig("merge.unityyamlmerge.trustExitCode", GitConfigSource.Local).Catch(e => {
+                Logger.Error(e, "Error removing merge.unityyamlmerge.trustExitCode");
+                return true;
+            }).RunSynchronously();
+
+            ConfigureMergeSettings();
+        }
+
         public void RestartRepository()
         {
             if (!Environment.RepositoryPath.IsInitialized)

src/GitHub.Api/Git/GitClient.cs

@@ -60,6 +60,15 @@ public interface IGitClient
         /// <returns>String output of git command</returns>
         ITask<string> SetConfig(string key, string value, GitConfigSource configSource, IOutputProcessor<string> processor = null);
 
+        /// <summary>
+        /// Executes `git config --unset` to remove a configuration value.
+        /// </summary>
+        /// <param name="key">The configuration key to remove</param>
+        /// <param name="configSource">The config source (unspecified, local,user,global) to use</param>
+        /// <param name="processor">A custom output processor instance</param>
+        /// <returns>String output of git command</returns>
+        ITask<string> UnSetConfig(string key, GitConfigSource configSource, IOutputProcessor<string> processor = null);
+
         /// <summary>
         /// Executes two `git config get` commands to get the git user and email.
         /// </summary>
@@ -367,6 +376,13 @@ public ITask<string> SetConfig(string key, string value, GitConfigSource configS
                 .Configure(processManager);
         }
 
+        ///<inheritdoc/>
+        public ITask<string> UnSetConfig(string key, GitConfigSource configSource, IOutputProcessor<string> processor = null)
+        {
+            return new GitConfigUnSetTask(key, configSource, cancellationToken, processor)
+                .Configure(processManager);
+        }
+
         ///<inheritdoc/>
         public ITask<GitUser> GetConfigUserAndEmail()
         {

src/GitHub.Api/Git/Tasks/GitConfigSetTask.cs

@@ -25,4 +25,4 @@ public GitConfigSetTask(string key, string value, GitConfigSource configSource,
         public override TaskAffinity Affinity { get { return TaskAffinity.Exclusive; } }
         public override string Message { get; set; } = "Writing configuration...";
     }
-}
+}

src/GitHub.Api/Git/Tasks/GitConfigUnSetTask.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Threading;
+
+namespace GitHub.Unity
+{
+    class GitConfigUnSetTask : ProcessTask<string>
+    {
+        private readonly string arguments;
+
+        public GitConfigUnSetTask(string key, GitConfigSource configSource,
+            CancellationToken token, IOutputProcessor<string> processor = null)
+            : base(token, processor ?? new SimpleOutputProcessor())
+        {
+            var source = "";
+            source +=
+                configSource == GitConfigSource.NonSpecified ? "--unset" :
+                configSource == GitConfigSource.Local ? "--local --unset" :
+                configSource == GitConfigSource.User ? "--global --unset" :
+                "--system --unset";
+            arguments = String.Format("config {0} {1}", source, key);
+            Name = String.Format("config {0} {1}", source, key);
+        }
+
+        public override string ProcessArguments { get { return arguments; } }
+        public override TaskAffinity Affinity { get { return TaskAffinity.Exclusive; } }
+        public override string Message { get; set; } = "Writing configuration...";
+    }
+}

src/GitHub.Api/GitHub.Api.45.csproj

@@ -82,6 +82,7 @@
     <Compile Include="Git\Tasks\GitCheckoutTask.cs" />
     <Compile Include="Git\GitAheadBehindStatus.cs" />
     <Compile Include="Git\Tasks\GitAheadBehindStatusTask.cs" />
+    <Compile Include="Git\Tasks\GitConfigUnSetTask.cs" />
     <Compile Include="Git\Tasks\GitCountObjectsTask.cs" />
     <Compile Include="Git\Tasks\GitLfsVersionTask.cs" />
     <Compile Include="Git\Tasks\GitVersionTask.cs" />

src/GitHub.Api/GitHub.Api.csproj

@@ -93,6 +93,7 @@
     <Compile Include="Git\Tasks\GitCheckoutTask.cs" />
     <Compile Include="Git\GitAheadBehindStatus.cs" />
     <Compile Include="Git\Tasks\GitAheadBehindStatusTask.cs" />
+    <Compile Include="Git\Tasks\GitConfigUnSetTask.cs" />
     <Compile Include="Git\Tasks\GitCountObjectsTask.cs" />
     <Compile Include="Git\Tasks\GitLfsVersionTask.cs" />
     <Compile Include="Git\Tasks\GitVersionTask.cs" />