enhance: warn users if they are using vimdiff or nvimdiff as external merge/diff tool (sourcegit-scm#1742)

Signed-off-by: leo <longshuang@msn.cn>

Author: love-linger

src/Commands/DiffTool.cs

@@ -17,12 +17,15 @@ public void Open()
             var tool = Native.OS.GetDiffMergeTool(true);
             if (tool == null)
             {
-                App.RaiseException(Context, "Invalid merge tool in preference setting!");
+                App.RaiseException(Context, "Invalid diff/merge tool in preference setting!");
                 return;
             }
 
             if (string.IsNullOrEmpty(tool.Cmd))
             {
+                if (!CheckGitConfiguration())
+                    return;
+
                 Args = $"difftool -g --no-prompt {_option}";
             }
             else
@@ -41,6 +44,34 @@ public void Open()
             }
         }
 
+        private bool CheckGitConfiguration()
+        {
+            var config = new Config(WorkingDirectory).ReadAll();
+            if (config.TryGetValue("diff.guitool", out var guiTool))
+                return CheckCLIBasedTool(guiTool);
+            if (config.TryGetValue("merge.guitool", out var mergeGuiTool))
+                return CheckCLIBasedTool(mergeGuiTool);
+            if (config.TryGetValue("diff.tool", out var diffTool))
+                return CheckCLIBasedTool(diffTool);
+            if (config.TryGetValue("merge.tool", out var mergeTool))
+                return CheckCLIBasedTool(mergeTool);
+
+            App.RaiseException(Context, "Missing git configuration: diff.guitool");
+            return false;
+        }
+
+        private bool CheckCLIBasedTool(string tool)
+        {
+            if (tool.StartsWith("vimdiff", StringComparison.Ordinal) ||
+                tool.StartsWith("nvimdiff", StringComparison.Ordinal))
+            {
+                App.RaiseException(Context, $"CLI based diff tool \"{tool}\" is not supported by this app!");
+                return false;
+            }
+
+            return true;
+        }
+
         private Models.DiffOption _option;
     }
 }

src/Commands/MergeTool.cs

@@ -1,4 +1,5 @@
-using System.Threading.Tasks;
+using System;
+using System.Threading.Tasks;
 
 namespace SourceGit.Commands
 {
@@ -16,13 +17,17 @@ public async Task<bool> OpenAsync()
             var tool = Native.OS.GetDiffMergeTool(false);
             if (tool == null)
             {
-                App.RaiseException(Context, "Invalid merge tool in preference setting!");
+                App.RaiseException(Context, "Invalid diff/merge tool in preference setting!");
                 return false;
             }
 
             if (string.IsNullOrEmpty(tool.Cmd))
             {
-                Args = $"mergetool {_file}";
+                var ok = await CheckGitConfigurationAsync();
+                if (!ok)
+                    return false;
+
+                Args = $"mergetool -g --no-prompt {_file}";
             }
             else
             {
@@ -33,6 +38,28 @@ public async Task<bool> OpenAsync()
             return await ExecAsync().ConfigureAwait(false);
         }
 
+        private async Task<bool> CheckGitConfigurationAsync()
+        {
+            var tool = await new Config(WorkingDirectory).GetAsync("merge.guitool");
+            if (string.IsNullOrEmpty(tool))
+                tool = await new Config(WorkingDirectory).GetAsync("merge.tool");
+
+            if (string.IsNullOrEmpty(tool))
+            {
+                App.RaiseException(Context, "Missing git configuration: merge.guitool");
+                return false;
+            }
+
+            if (tool.StartsWith("vimdiff", StringComparison.Ordinal) ||
+                tool.StartsWith("nvimdiff", StringComparison.Ordinal))
+            {
+                App.RaiseException(Context, $"CLI based merge tool \"{tool}\" is not supported by this app!");
+                return false;
+            }
+
+            return true;
+        }
+
         private string _file;
     }
 }