toxworkdir: use realpath

Fixes tox-dev#1169.

src/tox/config/__init__.py

@@ -999,6 +999,9 @@ def __init__(self, config, ini_path, ini_data):  # noqa
         else:
             config.toxworkdir = config.toxinidir.join(config.option.workdir, abs=True)
 
+        if os.path.exists(str(config.toxworkdir)):
+            config.toxworkdir = config.toxworkdir.realpath()
+
         if config.option.skip_missing_interpreters == "config":
             val = reader.getbool("skip_missing_interpreters", False)
             config.option.skip_missing_interpreters = "true" if val else "false"

tests/unit/config/test_config.py

@@ -279,6 +279,18 @@ def test_explicit_config_path(self, tmpdir):
         config = parseconfig(["-c", str(path)])
         assert config.toxinipath == config_file_path
 
+    @pytest.mark.skipif(sys.platform == "win32", reason="no symlinks on Windows")
+    def test_workdir_gets_resolved(self, tmpdir):
+        """
+        Test explicitly setting config path, both with and without the filename
+        """
+        real = tmpdir.mkdir("real")
+        symlink = tmpdir.join("link")
+        symlink.mksymlinkto(real)
+
+        config = parseconfig(["--workdir", str(symlink)])
+        assert config.toxworkdir == real
+
 
 def test_get_homedir(monkeypatch):
     monkeypatch.setattr(py.path.local, "_gethomedir", classmethod(lambda x: {}[1]))