repl: improve require() autocompletion

Currently REPL supports autocompletion for core modules and those found
in node_modules.  This commit adds tab completion for modules relative
to the current directory.

lib/repl.js

@@ -794,7 +794,18 @@ function complete(line, callback) {
     filter = match[1];
     var dir, files, f, name, base, ext, abs, subfiles, s;
     group = [];
-    var paths = module.paths.concat(Module.globalPaths);
+    let paths = [];
+
+    if (completeOn === '.') {
+      group = ['./', '../'];
+    } else if (completeOn === '..') {
+      group = ['../'];
+    } else if (/^\.\.?\//.test(completeOn)) {
+      paths = [process.cwd()];
+    } else {
+      paths = module.paths.concat(Module.globalPaths);
+    }
+
     for (i = 0; i < paths.length; i++) {
       dir = path.resolve(paths[i], subdir);
       try {

test/parallel/test-repl-tab-complete.js

@@ -232,6 +232,56 @@ testMe.complete('require(\'n', common.mustCall(function(error, data) {
   }));
 }
 
+// Test tab completion for require() relative to the current directory
+{
+  putIn.run(['.clear']);
+
+  const cwd = process.cwd();
+  process.chdir(__dirname);
+
+  ['require(\'.', 'require(".'].forEach((input) => {
+    testMe.complete(input, common.mustCall((err, data) => {
+      assert.strictEqual(err, null);
+      assert.strictEqual(data.length, 2);
+      assert.strictEqual(data[1], '.');
+      assert.strictEqual(data[0].length, 2);
+      assert.ok(data[0].includes('./'));
+      assert.ok(data[0].includes('../'));
+    }));
+  });
+
+  ['require(\'..', 'require("..'].forEach((input) => {
+    testMe.complete(input, common.mustCall((err, data) => {
+      assert.strictEqual(err, null);
+      assert.deepStrictEqual(data, [['../'], '..']);
+    }));
+  });
+
+  ['./', './test-'].forEach((path) => {
+    [`require('${path}`, `require("${path}`].forEach((input) => {
+      testMe.complete(input, common.mustCall((err, data) => {
+        assert.strictEqual(err, null);
+        assert.strictEqual(data.length, 2);
+        assert.strictEqual(data[1], path);
+        assert.ok(data[0].includes('./test-repl-tab-complete'));
+      }));
+    });
+  });
+
+  ['../parallel/', '../parallel/test-'].forEach((path) => {
+    [`require('${path}`, `require("${path}`].forEach((input) => {
+      testMe.complete(input, common.mustCall((err, data) => {
+        assert.strictEqual(err, null);
+        assert.strictEqual(data.length, 2);
+        assert.strictEqual(data[1], path);
+        assert.ok(data[0].includes('../parallel/test-repl-tab-complete'));
+      }));
+    });
+  });
+
+  process.chdir(cwd);
+}
+
 // Make sure tab completion works on context properties
 putIn.run(['.clear']);