feat(config): add ability to get value(s) of multivar variable

lib/src/bindings/config.dart

@@ -247,8 +247,36 @@ void deleteVariable(Pointer<git_config> cfg, String name) {
   }
 }
 
-/// Iterate over the values of multivar
-// TODO
+/// Iterate over the values of a multivar
+///
+/// If regexp is present, then the iterator will only iterate over all
+/// values which match the pattern.
+List<String> getMultivar(
+  Pointer<git_config> cfg,
+  String name,
+  String? regexp,
+) {
+  final nameC = name.toNativeUtf8().cast<Int8>();
+  final regexpC = regexp?.toNativeUtf8().cast<Int8>() ?? nullptr;
+  final iterator = calloc<Pointer<git_config_iterator>>();
+  final entry = calloc<Pointer<git_config_entry>>();
+  libgit2.git_config_multivar_iterator_new(iterator, cfg, nameC, regexpC);
+  var error = 0;
+  final entries = <String>[];
 
-/// Multivars variables get/set
-// TODO
+  while (error == 0) {
+    error = libgit2.git_config_next(entry, iterator.value);
+    if (error != -31) {
+      entries.add(entry.value.ref.value.cast<Utf8>().toDartString());
+    } else {
+      break;
+    }
+  }
+
+  calloc.free(nameC);
+  calloc.free(regexpC);
+  calloc.free(iterator);
+  calloc.free(entry);
+
+  return entries;
+}

lib/src/config.dart

@@ -142,6 +142,14 @@ class Config {
     }
   }
 
+  /// Returns list of values for multivar [key]
+  ///
+  /// If [regexp] is present, then the iterator will only iterate over all
+  /// values which match the pattern.
+  List<String> getMultivar(String key, {String? regexp}) {
+    return config.getMultivar(configPointer.value, key, regexp);
+  }
+
   /// Releases memory allocated for config object.
   void close() {
     calloc.free(configPointer);

test/config_test.dart

@@ -8,6 +8,16 @@ import 'package:libgit2dart/src/error.dart';
 void main() {
   final tmpDir = Directory.systemTemp.path;
   const configFileName = 'test_config';
+  const contents = '''
+[core]
+  repositoryformatversion = 0
+  bare = false
+  gitproxy = proxy-command for kernel.org
+  gitproxy = default-proxy
+[remote "origin"]
+  url = someurl
+''';
+
   late Config config;
 
   group('Config', () {
@@ -16,8 +26,7 @@ void main() {
     });
 
     setUp(() {
-      File('$tmpDir/$configFileName').writeAsStringSync(
-          '[core]\n\trepositoryformatversion = 0\n\tbare = false\n[remote "origin"]\n\turl = someurl');
+      File('$tmpDir/$configFileName').writeAsStringSync(contents);
       config = Config.open(path: '$tmpDir/$configFileName');
     });
 
@@ -64,6 +73,23 @@ void main() {
         throwsA(isA<LibGit2Error>()),
       );
     });
+
+    test('returns values of multivar', () {
+      expect(
+        config.getMultivar('core.gitproxy'),
+        [
+          'proxy-command for kernel.org',
+          'default-proxy',
+        ],
+      );
+    });
+
+    test('returns values of multivar with regexp', () {
+      expect(
+        config.getMultivar('core.gitproxy', regexp: 'for kernel.org\$'),
+        ['proxy-command for kernel.org'],
+      );
+    });
   });
   ;
 }