Add the config arg --eval-attr

Nose users will get confused by using the -a argument which
uses eval-like syntax while in nose-attrib that arg uses
a different approach. Hence, we add a --eval-attr argument
which allows users to be compatible with both.

Fixes #7

pytest_attrib/plugin.py

@@ -5,7 +5,7 @@
 
 def pytest_addoption(parser):
     group = parser.getgroup("general")
-    group._addoption("-a", action="store", default="",
+    group._addoption("--eval-attr", "-a", action="store", default="",
                      dest="attrexpr", metavar="ATTREXPR",
                      help='Only run tests matching given attribute expression.'
                           '  Example: -a "attr1==val1 and attr2==val2".')

tests/test_attrib.py

@@ -22,6 +22,9 @@ def test_arg(testdir):
     result = testdir.runpytest("--help")
     result.stdout.fnmatch_lines("*-a ATTREXPR*")
 
+    result = testdir.runpytest("--help")
+    result.stdout.fnmatch_lines("*--eval-attr=ATTREXPR*")
+
 
 def test_config(testdir):
     config = testdir.parseconfig()
@@ -38,6 +41,21 @@ def test_config(testdir):
     assert config.getoption('attrexpr') == 'attr1==val1 and attr2==True'
 
 
+def test_long_config(testdir):
+    config = testdir.parseconfig()
+    assert config.getoption('attrexpr') == ''
+
+    config = testdir.parseconfig('--eval-attr', 'attr1')
+    assert config.getoption('attrexpr') == 'attr1'
+
+    config = testdir.parseconfig('--eval-attr', 'attr1==val1 and attr2==True')
+    assert config.getoption('attrexpr') == 'attr1==val1 and attr2==True'
+
+    config = testdir.parseconfig('--eval-attr', 'attr1==val1 and attr2==True',
+                                 '-k', 'somethingelse')
+    assert config.getoption('attrexpr') == 'attr1==val1 and attr2==True'
+
+
 @pytest.mark.parametrize("spec", [
     ("xyz", ("test_one",)),
     ("xyz and xyz2", ()),