feat(repository): add ability to check status of repo and single file

lib/src/bindings/status.dart

@@ -0,0 +1,81 @@
+import 'dart:ffi';
+import 'package:ffi/ffi.dart';
+import 'package:libgit2dart/libgit2dart.dart';
+import 'libgit2_bindings.dart';
+import '../error.dart';
+import '../util.dart';
+
+/// Gather file status information and populate the git_status_list.
+///
+/// Throws a [LibGit2Error] if error occured.
+Pointer<git_status_list> listNew(Pointer<git_repository> repo) {
+  final out = calloc<Pointer<git_status_list>>();
+  final error = libgit2.git_status_list_new(out, repo, nullptr);
+
+  if (error < 0) {
+    throw LibGit2Error(libgit2.git_error_last());
+  } else {
+    return out.value;
+  }
+}
+
+/// Gets the count of status entries in this list.
+///
+/// If there are no changes in status (at least according the options given when
+/// the status list was created), this can return 0.
+int listEntryCount(Pointer<git_status_list> statuslist) {
+  return libgit2.git_status_list_entrycount(statuslist);
+}
+
+/// Get a pointer to one of the entries in the status list.
+///
+/// The entry is not modifiable and should not be freed.
+///
+/// Throws [RangeError] if position is out of bounds
+Pointer<git_status_entry> getByIndex(
+  Pointer<git_status_list> statuslist,
+  int idx,
+) {
+  final result = libgit2.git_status_byindex(statuslist, idx);
+
+  if (result == nullptr) {
+    throw RangeError('Out of bounds');
+  } else {
+    return result;
+  }
+}
+
+/// Get file status for a single file.
+///
+/// This tries to get status for the filename that you give. If no files match that name
+/// (in either the HEAD, index, or working directory), this returns GIT_ENOTFOUND.
+///
+/// If the name matches multiple files (for example, if the path names a directory or if
+/// running on a case- insensitive filesystem and yet the HEAD has two entries that both
+/// match the path), then this returns GIT_EAMBIGUOUS because it cannot give correct results.
+///
+/// This does not do any sort of rename detection. Renames require a set of targets and because
+/// of the path filtering, there is not enough information to check renames correctly. To check
+/// file status with rename detection, there is no choice but to do a full listNew
+/// and scan through looking for the path that you are interested in.
+///
+/// Throws a [LibGit2Error] if error occured.
+int file(Pointer<git_repository> repo, String path) {
+  final out = calloc<Uint32>();
+  final pathC = path.toNativeUtf8().cast<Int8>();
+  final error = libgit2.git_status_file(out, repo, pathC);
+
+  calloc.free(pathC);
+
+  if (error < 0) {
+    throw LibGit2Error(libgit2.git_error_last());
+  } else {
+    final result = out.value;
+    calloc.free(out);
+    return result;
+  }
+}
+
+/// Free an existing status list.
+void listFree(Pointer<git_status_list> statuslist) =>
+    libgit2.git_status_list_free(statuslist);