feat(diff): add binding and API method for git_diff_tree_to_workdir_with_index (#23)

lib/src/bindings/diff.dart

@@ -89,6 +89,44 @@ Pointer<git_diff> treeToWorkdir({
   return out.value;
 }
 
+/// Create a diff between a tree and the working directory using index data to
+/// account for staged deletes, tracked files, etc.
+///
+/// This emulates `git diff <tree>` by diffing the tree to the index and the
+/// index to the working directory and blending the results into a single diff
+/// that includes staged deleted, etc.
+///
+/// Throws a [LibGit2Error] if error occured.
+Pointer<git_diff> treeToWorkdirWithIndex({
+  required Pointer<git_repository> repoPointer,
+  required Pointer<git_tree>? treePointer,
+  required int flags,
+  required int contextLines,
+  required int interhunkLines,
+}) {
+  final out = calloc<Pointer<git_diff>>();
+  final opts = _diffOptionsInit(
+    flags: flags,
+    contextLines: contextLines,
+    interhunkLines: interhunkLines,
+  );
+
+  final error = libgit2.git_diff_tree_to_workdir_with_index(
+    out,
+    repoPointer,
+    treePointer ?? nullptr,
+    opts,
+  );
+
+  if (error < 0) {
+    throw LibGit2Error(libgit2.git_error_last());
+  }
+
+  calloc.free(opts);
+
+  return out.value;
+}
+
 /// Create a diff with the difference between two tree objects.
 ///
 /// Throws a [LibGit2Error] if error occured.

lib/src/diff.dart

@@ -14,6 +14,44 @@ class Diff {
   /// **IMPORTANT**: Should be freed to release allocated memory.
   Diff(this._diffPointer);
 
+  /// Creates a diff between a [tree] and the working directory using index
+  /// data to account for staged deletes, tracked files, etc.
+  ///
+  /// This emulates `git diff <tree>` by diffing the tree to the index and the
+  /// index to the working directory and blending the results into a single diff
+  /// that includes staged deleted, etc.
+  ///
+  /// [repo] is the repository containing the tree.
+  ///
+  /// [tree] is a [Tree] object to diff from, or null for empty tree.
+  ///
+  /// [flags] is a combination of [GitDiff] flags. Defaults to [GitDiff.normal].
+  ///
+  /// [contextLines] is the number of unchanged lines that define the boundary
+  /// of a hunk (and to display before and after). Defaults to 3.
+  ///
+  /// [interhunkLines] is the maximum number of unchanged lines between hunk
+  /// boundaries before the hunks will be merged into one. Defaults to 0.
+  ///
+  /// **IMPORTANT**: Should be freed to release allocated memory.
+  ///
+  /// Throws a [LibGit2Error] if error occured.
+  Diff.treeToWorkdirWithIndex({
+    required Repository repo,
+    required Tree? tree,
+    Set<GitDiff> flags = const {GitDiff.normal},
+    int contextLines = 3,
+    int interhunkLines = 0,
+  }) {
+    _diffPointer = bindings.treeToWorkdirWithIndex(
+      repoPointer: repo.pointer,
+      treePointer: tree?.pointer,
+      flags: flags.fold(0, (acc, e) => acc | e.value),
+      contextLines: contextLines,
+      interhunkLines: interhunkLines,
+    );
+  }
+
   /// Reads the [content]s of a git patch file into a git diff object.
   ///
   /// The diff object produced is similar to the one that would be produced if