refactor: Split packagesettings module into a package

The `packagesettings` module has grown to over 1,200 lines of code. With
upcoming plans to improve resolver, downloader, and patching, the code
is going to grow even more.

Split the module into a package with several private modules. The public
interface of the `fromager.packagesettings` is mostly staying the same.
Only one monkey-patching case for testing had to be changed.

Co-Authored-By: Claude <claude@anthropic.com>

Signed-off-by: Christian Heimes <cheimes@redhat.com>

Author: tiran

src/fromager/packagesettings.py

@@ -0,0 +1,59 @@
+"""Package settings for Fromager build system."""
+
+from ._hooks import default_update_extra_environ, get_extra_environ
+from ._models import (
+    BuildOptions,
+    DownloadSource,
+    GitOptions,
+    PackageSettings,
+    ProjectOverride,
+    ResolverDist,
+    VariantInfo,
+)
+from ._pbi import PackageBuildInfo
+from ._settings import Settings, SettingsFile
+from ._templates import substitute_template
+from ._typedefs import (
+    MODEL_CONFIG,
+    Annotations,
+    BuildDirectory,
+    EnvKey,
+    EnvVars,
+    GlobalChangelog,
+    Package,
+    PackageVersion,
+    PatchMap,
+    RawAnnotations,
+    Template,
+    Variant,
+    VariantChangelog,
+)
+
+__all__ = (
+    "MODEL_CONFIG",
+    "Annotations",
+    "BuildDirectory",
+    "BuildOptions",
+    "DownloadSource",
+    "EnvKey",
+    "EnvVars",
+    "GitOptions",
+    "GlobalChangelog",
+    "Package",
+    "PackageBuildInfo",
+    "PackageSettings",
+    "PackageVersion",
+    "PatchMap",
+    "ProjectOverride",
+    "RawAnnotations",
+    "ResolverDist",
+    "Settings",
+    "SettingsFile",
+    "Template",
+    "Variant",
+    "VariantChangelog",
+    "VariantInfo",
+    "default_update_extra_environ",
+    "get_extra_environ",
+    "substitute_template",
+)

src/fromager/packagesettings/__init__.py

@@ -0,0 +1,55 @@
+"""Hook functions for extra environment variable management."""
+
+from __future__ import annotations
+
+import pathlib
+import typing
+
+from packaging.requirements import Requirement
+from packaging.version import Version
+
+from .. import overrides
+
+if typing.TYPE_CHECKING:
+    from .. import build_environment, context
+
+
+def default_update_extra_environ(
+    *,
+    ctx: context.WorkContext,
+    req: Requirement,
+    version: Version | None,
+    sdist_root_dir: pathlib.Path,
+    extra_environ: dict[str, str],
+    build_env: build_environment.BuildEnvironment,
+) -> None:
+    """Update extra_environ in-place"""
+    return None
+
+
+def get_extra_environ(
+    *,
+    ctx: context.WorkContext,
+    req: Requirement,
+    version: Version | None,
+    sdist_root_dir: pathlib.Path,
+    build_env: build_environment.BuildEnvironment,
+) -> dict[str, str]:
+    """Get extra environment variables from settings and update hook"""
+    pbi = ctx.package_build_info(req)
+    extra_environ = pbi.get_extra_environ(
+        build_env=build_env,
+        version=version,
+    )
+    overrides.find_and_invoke(
+        req.name,
+        "update_extra_environ",
+        default_update_extra_environ,
+        ctx=ctx,
+        req=req,
+        version=version,
+        sdist_root_dir=sdist_root_dir,
+        extra_environ=extra_environ,
+        build_env=build_env,
+    )
+    return extra_environ