Add Cirrus CI to CIProvider enum

cibuildwheel/__main__.py

@@ -160,9 +160,9 @@ def build_in_directory(args: CommandLineArguments) -> None:
                 textwrap.dedent(
                     """
                     cibuildwheel: Unable to detect platform. cibuildwheel should run on your CI server;
-                    Travis CI, AppVeyor, Azure Pipelines, GitHub Actions, CircleCI, and Gitlab are
+                    Travis CI, AppVeyor, Azure Pipelines, GitHub Actions, CircleCI, Gitlab, and Cirrus CI
-                    supported. You can run on your development machine or other CI providers using the
+                    are supported. You can run on your development machine or other CI providers
-                    --platform argument. Check --help output for more information.
+                    using the --platform argument. Check --help output for more information.
                     """
                 ),
                 file=sys.stderr,

cibuildwheel/linux.py

@@ -349,6 +349,8 @@ def build(options: Options, tmp_path: Path) -> None:  # pylint: disable=unused-a
                 If you're building on Travis CI, add `services: [docker]` to
                 your .travis.yml. If you're building on Circle CI in Linux,
                 add a `setup_remote_docker` step to your .circleci/config.yml.
+                If you're building on Cirrus CI, use `docker_builder` task on x86
+                or run `docker:dind` image in an additional container on ARM.
                 """
             ),
             file=sys.stderr,

cibuildwheel/util.py

@@ -393,6 +393,7 @@ class CIProvider(Enum):
     azure_pipelines = "azure_pipelines"
     github_actions = "github_actions"
     gitlab = "gitlab"
+    cirrus_ci = "cirrus_ci"
     other = "other"
 
 
@@ -409,6 +410,8 @@ def detect_ci_provider() -> CIProvider | None:
         return CIProvider.github_actions
     elif "GITLAB_CI" in os.environ:
         return CIProvider.gitlab
+    elif "CIRRUS_CI" in os.environ:
+        return CIProvider.cirrus_ci
     elif strtobool(os.environ.get("CI", "false")):
         return CIProvider.other
     else:

unit_test/main_tests/main_platform_test.py

@@ -19,6 +19,7 @@ def test_unknown_platform_non_ci(monkeypatch, capsys):
     monkeypatch.delenv("GITHUB_ACTIONS", raising=False)
     monkeypatch.delenv("GITLAB_CI", raising=False)
     monkeypatch.delenv("CIRCLECI", raising=False)
+    monkeypatch.delenv("CIRRUS_CI", raising=False)
     monkeypatch.delenv("CIBW_PLATFORM", raising=False)
 
     with pytest.raises(SystemExit) as exit: