refactor: Override options redesign

* Add test for defaults, fix platform detection

* Improve correctness of reader.identifier with block

* Fix options test to be multiplatform

* 'Refactored by Sourcery'

docs: write a section on overrides

tests: test docker launches

feat: add identifiers to launches

test: add test for correct build step generation

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

unit_test/options_test.py

@@ -0,0 +1,68 @@
+import platform as platform_module
+
+from cibuildwheel.__main__ import get_build_identifiers
+from cibuildwheel.environment import parse_environment
+from cibuildwheel.options import Options, _get_pinned_docker_images
+
+from .utils import get_default_command_line_arguments
+
+PYPROJECT_1 = """
+[tool.cibuildwheel]
+build = ["cp38*", "cp37*"]
+environment = {FOO="BAR"}
+
+test-command = "pyproject"
+
+manylinux-x86_64-image = "manylinux1"
+
+[tool.cibuildwheel.macos]
+test-requires = "else"
+
+[[tool.cibuildwheel.overrides]]
+select = "cp37*"
+test-command = "pyproject-override"
+manylinux-x86_64-image = "manylinux2014"
+"""
+
+
+def test_options_1(tmp_path, monkeypatch):
+    with tmp_path.joinpath("pyproject.toml").open("w") as f:
+        f.write(PYPROJECT_1)
+
+    args = get_default_command_line_arguments()
+    args.package_dir = str(tmp_path)
+
+    monkeypatch.setattr(platform_module, "machine", lambda: "x86_64")
+
+    options = Options(platform="linux", command_line_arguments=args)
+
+    identifiers = get_build_identifiers(
+        platform="linux",
+        build_selector=options.globals.build_selector,
+        architectures=options.globals.architectures,
+    )
+
+    override_display = """\
+test_command: 'pyproject'
+  cp37-manylinux_x86_64: 'pyproject-override'"""
+
+    print(options.summary(identifiers))
+
+    assert override_display in options.summary(identifiers)
+
+    default_build_options = options.build_options(identifier=None)
+
+    assert default_build_options.environment == parse_environment('FOO="BAR"')
+
+    all_pinned_docker_images = _get_pinned_docker_images()
+    pinned_x86_64_docker_image = all_pinned_docker_images["x86_64"]
+
+    local = options.build_options("cp38-manylinux_x86_64")
+    assert local.manylinux_images is not None
+    assert local.test_command == "pyproject"
+    assert local.manylinux_images["x86_64"] == pinned_x86_64_docker_image["manylinux1"]
+
+    local = options.build_options("cp37-manylinux_x86_64")
+    assert local.manylinux_images is not None
+    assert local.test_command == "pyproject-override"
+    assert local.manylinux_images["x86_64"] == pinned_x86_64_docker_image["manylinux2014"]