Pass filename to Flake8

Pass the filename as the argument "stdin-display-name".
Change the working directory where flask8 is executed to the same directory as the configuration file. This ensures that relative patterns defined in the configuration file work properly.
Add test.

This commit implements #454

lib/main.js

@@ -173,14 +173,15 @@ export default {
             parameters.push('--builtins', this.builtins.join(','));
           }
         }
+        parameters.push('--stdin-display-name', filePath);
 
         parameters.push('-');
 
         const execPath = fs.normalize(applySubstitutions(this.executablePath, baseDir));
         const forceTimeout = 1000 * 60 * 5; // (ms * s * m) = Five minutes
         const options = {
           stdin: fileText,
-          cwd: path.dirname(textEditor.getPath()),
+          cwd: baseDir,
           ignoreExitCode: true,
           timeout: forceTimeout,
           uniqueKey: `linter-flake8:${filePath}`,

spec/fixtures/with-config-file/bad-ignored.py

@@ -0,0 +1 @@
+asfd

spec/fixtures/with-config-file/subdir/bad-ignored.py

@@ -0,0 +1 @@
+asfd

spec/fixtures/with-config-file/tox.ini

@@ -0,0 +1,2 @@
+[flake8]
+exclude = bad-ignored.py, subdir/bad-ignored.py

spec/linter-flake8-spec.js

@@ -6,8 +6,11 @@ import { beforeEach, it } from 'jasmine-fix';
 // NOTE: If using fit you must add it to the list above!
 
 const fixturePath = join(__dirname, 'fixtures');
+const fixtureWithConfigPath = join(__dirname, 'fixtures', 'with-config-file');
 const goodPath = join(fixturePath, 'good.py');
 const badPath = join(fixturePath, 'bad.py');
+const badIgnoredPath = join(fixtureWithConfigPath, 'bad-ignored.py');
+const badSubdirIgnoredPath = join(fixtureWithConfigPath, 'subdir', 'bad-ignored.py');
 const errwarnPath = join(fixturePath, 'errwarn.py');
 const builtinsPath = join(fixturePath, 'builtins.py');
 
@@ -86,6 +89,26 @@ describe('The flake8 provider for Linter', () => {
     });
   });
 
+  describe('use configuration file and', () => {
+    let editor = null;
+
+    beforeEach(async () => {
+      atom.project.addPath(fixtureWithConfigPath);
+      editor = await atom.workspace.open(badIgnoredPath);
+    });
+
+    it('ignores file excluded in configuration file', async () => {
+      const messages = await lint(editor);
+      expect(messages.length).toBe(0);
+    });
+
+    it('ignores file excluded in configuration file using relative path', async () => {
+      editor = await atom.workspace.open(badSubdirIgnoredPath);
+      const messages = await lint(editor);
+      expect(messages.length).toBe(0);
+    });
+  });
+
   it('finds nothing wrong with a valid file', async () => {
     const editor = await atom.workspace.open(goodPath);
     const messages = await lint(editor);