Add ability to exclude files matching glob patterns in conftest.py

This adds the `collect_ignore_glob` option for `conftest.py` to allow
Unix-style wildcards for excluding files.

changelog/3711.feature.rst

@@ -1 +1,2 @@
 Add the ``--ignore-glob`` parameter to exclude test-modules with Unix shell-style wildcards.
+Add the ``collect_ignore_glob`` for ``conftest.py`` to exclude test-modules with Unix shell-style wildcards.

doc/en/example/pythoncollection.rst

@@ -269,3 +269,17 @@ file will be left out:
     collected 0 items
 
     ======================= no tests ran in 0.12 seconds =======================
+
+It's also possible to ignore files based on Unix shell-style wildcards by adding
+patterns to ``collect_ignore_glob``.
+
+The following example ``conftest.py`` ignores the file ``setup.py`` and in
+addition all files that end with ``*_py2.py`` when executed with a Python 3
+interpreter::
+
+    # content of conftest.py
+    import sys
+
+    collect_ignore = ["setup.py"]
+    if sys.version_info[0] > 2:
+        collect_ignore_glob = ["*_py2.py"]

src/_pytest/main.py

@@ -303,7 +303,10 @@ def pytest_ignore_collect(path, config):
     if py.path.local(path) in ignore_paths:
         return True
 
-    ignore_globs = []
+    ignore_globs = config._getconftest_pathlist(
+        "collect_ignore_glob", path=path.dirpath()
+    )
+    ignore_globs = ignore_globs or []
     excludeglobopt = config.getoption("ignore_glob")
     if excludeglobopt:
         ignore_globs.extend([py.path.local(x) for x in excludeglobopt])

testing/test_collection.py

@@ -374,6 +374,26 @@ class TestCustomConftests(object):
         assert result.ret == 0
         assert "passed" in result.stdout.str()
 
+    def test_collectignoreglob_exclude_on_option(self, testdir):
+        testdir.makeconftest(
+            """
+            collect_ignore_glob = ['*w*l[dt]*']
+            def pytest_addoption(parser):
+                parser.addoption("--XX", action="store_true", default=False)
+            def pytest_configure(config):
+                if config.getvalue("XX"):
+                    collect_ignore_glob[:] = []
+        """
+        )
+        testdir.makepyfile(test_world="def test_hello(): pass")
+        testdir.makepyfile(test_welt="def test_hallo(): pass")
+        result = testdir.runpytest()
+        assert result.ret == EXIT_NOTESTSCOLLECTED
+        result.stdout.fnmatch_lines("*collected 0 items*")
+        result = testdir.runpytest("--XX")
+        assert result.ret == 0
+        result.stdout.fnmatch_lines("*2 passed*")
+
     def test_pytest_fs_collect_hooks_are_seen(self, testdir):
         testdir.makeconftest(
             """