Improved IsConflicResolved check, to work for submodule conflicts

Author: goran-w

src/Commands/IsConflictResolved.cs

@@ -2,18 +2,38 @@
 {
     public class IsConflictResolved : Command
     {
+        private string StatusArgs;
+        private string DiffArgs;
+
         public IsConflictResolved(string repo, Models.Change change)
         {
             var opt = new Models.DiffOption(change, true);
 
             WorkingDirectory = repo;
             Context = repo;
-            Args = $"diff -a --ignore-cr-at-eol --check {opt}";
+
+            StatusArgs = $"--no-optional-locks status --porcelain=v2 -- \"{change.Path}\"";
+            DiffArgs = $"diff -a --ignore-cr-at-eol --check {opt}";
         }
 
         public bool Result()
         {
-            return ReadToEnd().IsSuccess;
+            // First, check if the file is still "unmerged"...
+            Args = StatusArgs;
+            var rs = ReadToEnd();
+            if (rs.IsSuccess && rs.StdOut.StartsWith("u"))
+            {
+                // Then, check if the file is a submodule (then we can't use a text-diff).
+                // Porcelain Format Version 2, Unmerged entry: "u <XY> <N|S><c><m><u> <...>"
+                if (rs.StdOut.Substring(5, 1) == "S")
+                    return false;
+
+                // Finally, run a text-diff, checking for conflict-markers.
+                // (NOTE: Could possibly give false positives for whitespace errors?)
+                Args = DiffArgs;
+                return ReadToEnd().IsSuccess;
+            }
+            return true;
         }
     }
 }