bdd_features_base_dir is relative to pytest rootdir

The pytest rootdir is the directory containing pytest.ini (or similar):
https://docs.pytest.org/en/latest/reference/customize.html#rootdir

This allows you to run pytest when the current working directory isn't
the same as the directory containing the tests. I need to do that
because in my system, the directory containing the tests is on a
read-only filesystem.

README.rst

@@ -801,7 +801,7 @@ then
 Feature file paths
 ------------------
 
-By default, pytest-bdd will use current module's path as base path for finding feature files, but this behaviour can be changed in the pytest configuration file (i.e. `pytest.ini`, `tox.ini` or `setup.cfg`) by declaring the new base path in the `bdd_features_base_dir` key. The path is interpreted as relative to the working directory when starting pytest.
+By default, pytest-bdd will use current module's path as base path for finding feature files, but this behaviour can be changed in the pytest configuration file (i.e. `pytest.ini`, `tox.ini` or `setup.cfg`) by declaring the new base path in the `bdd_features_base_dir` key. The path is interpreted as relative to the `pytest root directory <https://docs.pytest.org/en/latest/reference/customize.html#rootdir>`__.
 You can also override features base path on a per-scenario basis, in order to override the path for specific tests.
 
 pytest.ini:

src/pytest_bdd/scenario.py

@@ -287,8 +287,11 @@ def scenario(
 
 
 def get_features_base_dir(caller_module_path: str) -> str:
-    default_base_dir = os.path.dirname(caller_module_path)
-    return get_from_ini("bdd_features_base_dir", default_base_dir)
+    d = get_from_ini("bdd_features_base_dir", None)
+    if d is None:
+        return os.path.dirname(caller_module_path)
+    rootdir = CONFIG_STACK[-1].rootpath
+    return os.path.join(rootdir, d)
 
 
 def get_from_ini(key: str, default: str) -> str:

tests/feature/test_feature_base_dir.py

@@ -1,4 +1,6 @@
 """Test feature base dir."""
+import os
+
 import pytest
 
 NOT_EXISTING_FEATURE_PATHS = [".", "/does/not/exist/"]
@@ -21,6 +23,19 @@ def test_feature_path_ok(pytester):
     result.assert_outcomes(passed=2)
 
 
+def test_feature_path_ok_running_outside_rootdir(pytester):
+    base_dir = "features"
+    prepare_testdir(pytester, base_dir)
+
+    old_dir = os.getcwd()
+    os.chdir("/")
+    try:
+        result = pytester.runpytest(pytester.path, "-k", "test_ok_by_ini")
+        result.assert_outcomes(passed=2)
+    finally:
+        os.chdir(old_dir)
+
+
 def test_feature_path_by_param_not_found(pytester):
     """As param takes precedence even if ini config is correct it should fail
     if passed param is incorrect"""