make tmpdir fixture always return a realpath()ed tmpdir and make a note

about it in the changed test.  Currently, i don't see a reason why this
is a bad idea (tm)

_pytest/__init__.py

@@ -1,2 +1,2 @@
 #
-__version__ = '2.3.0.dev21'
+__version__ = '2.3.0.dev22'

_pytest/tmpdir.py

@@ -40,7 +40,7 @@ class TempdirHandler:
                 basetemp.mkdir()
             else:
                 basetemp = py.path.local.make_numbered_dir(prefix='pytest-')
-            self._basetemp = t = basetemp
+            self._basetemp = t = basetemp.realpath()
             self.trace("new basetemp", t)
             return t
 

setup.py

@@ -24,7 +24,7 @@ def main():
         name='pytest',
         description='py.test: simple powerful testing with Python',
         long_description = long_description,
-        version='2.3.0.dev21',
+        version='2.3.0.dev22',
         url='http://pytest.org',
         license='MIT license',
         platforms=['unix', 'linux', 'osx', 'cygwin', 'win32'],

testing/test_tmpdir.py

@@ -72,14 +72,21 @@ def test_basetemp(testdir):
     assert mytemp.join('hello').check()
 
 @pytest.mark.skipif("not hasattr(py.path.local, 'mksymlinkto')")
-def test_tmpdir_keeps_symlinks(testdir):
+def test_tmpdir_always_is_realpath(testdir):
+    # the reason why tmpdir should be a realpath is that
+    # when you cd to it and do "os.getcwd()" you will anyway
+    # get the realpath.  Using the symlinked path can thus
+    # easily result in path-inequality
+    # XXX if that proves to be a problem, consider using
+    # os.environ["PWD"]
     realtemp = testdir.tmpdir.mkdir("myrealtemp")
     linktemp = testdir.tmpdir.join("symlinktemp")
     linktemp.mksymlinkto(realtemp)
     p = testdir.makepyfile("""
         def test_1(tmpdir):
             import os
-            assert os.path.realpath(str(tmpdir)) != str(tmpdir)
+            assert os.path.realpath(str(tmpdir)) == str(tmpdir)
     """)
     result = testdir.runpytest("-s", p, '--basetemp=%s/bt' % linktemp)
     assert not result.ret
+