if _options.basedir exists, use it in external, exclude and ignore

Adding test for external basedir case

index.js

@@ -252,23 +252,23 @@ Browserify.prototype.external = function (file, opts) {
     }
 
     if (!opts) opts = {};
-    var basedir = defined(opts.basedir, process.cwd());
+    var basedir = defined(opts.basedir, self._options.basedir, process.cwd());
     this._external.push(file);
     this._external.push('/' + path.relative(basedir, file));
     return this;
 };
 
 Browserify.prototype.exclude = function (file, opts) {
     if (!opts) opts = {};
-    var basedir = defined(opts.basedir, process.cwd());
+    var basedir = defined(opts.basedir, this._options.basedir, process.cwd());
     this._exclude.push(file);
     this._exclude.push('/' + path.relative(basedir, file));
     return this;
 };
 
 Browserify.prototype.ignore = function (file, opts) {
     if (!opts) opts = {};
-    var basedir = defined(opts.basedir, process.cwd());
+    var basedir = defined(opts.basedir, this._options.basedir, process.cwd());
 
     // Handle relative paths
     if (file[0] === '.') {

test/external_basedir.js

@@ -0,0 +1,39 @@
+var browserify = require('../');
+var vm = require('vm');
+var test = require('tap').test;
+
+test('external', function (t) {
+    t.plan(2);
+    var baseDir = __dirname;
+    var splitFile = baseDir + '/external_basedir/y.js';
+    var mainSrc = '';
+    var splitSrc = '';
+    var pending = 2;
+
+    // main bundle should not include splitFile
+    var b = browserify(baseDir + '/external_basedir/main.js', {basedir: baseDir});
+    b.external(splitFile); // no need to specify basedir option if it is already set for b
+    b.bundle(function (err, src) {
+        if (err) return t.fail(err);
+        mainSrc = src;
+        pending--;
+        done();
+    });
+
+    // consider b2 as for split or vendor bundle
+    var b2 = browserify([], {basedir: baseDir});
+    b2.require(splitFile, {expose: splitFile.replace(baseDir, '')});
+    b2.bundle(function (err, src) {
+        if (err) return t.fail(err);
+        splitSrc = src;
+        pending--;
+        done();
+    });
+
+    function done() {
+        if (pending !== 0) {
+            return;
+        }
+        vm.runInNewContext(splitSrc + mainSrc, { t: t });
+    }
+});

test/external_basedir/main.js

@@ -0,0 +1,2 @@
+t.equal(require('./x'), 'foo');
+t.equal(require('./y'), 'bar');

test/external_basedir/x.js

@@ -0,0 +1 @@
+module.exports = 'foo';

test/external_basedir/y.js

@@ -0,0 +1 @@
+module.exports = 'bar';