feat(ci): add --config option and MERGIFY_CONFIG envvar to git-refs and scopes

Allow passing the mergify config file path via --config flag or
MERGIFY_CONFIG environment variable for both ci git-refs and ci scopes
commands.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Change-Id: Ide4525c9098103cd36627bf592518ba11c8d9c9c

Author: sileht

mergify_cli/ci/cli.py

@@ -204,7 +204,15 @@ async def junit_process(
     help="""Give the base/head git references of the pull request""",
     short_help="""Give the base/head git references of the pull request""",
 )
-def git_refs() -> None:
+@click.option(
+    "--config",
+    "config_path",
+    type=click.Path(),
+    envvar="MERGIFY_CONFIG",
+    default=detector.get_mergify_config_path,
+    help="Path to YAML config file.",
+)
+def git_refs(config_path: str | None) -> None:
     ref = git_refs_detector.detect()
     click.echo(f"Base: {ref.base}")
     click.echo(f"Head: {ref.head}")
@@ -219,6 +227,7 @@ def git_refs() -> None:
     "--config",
     "config_path",
     type=click.Path(),
+    envvar="MERGIFY_CONFIG",
     default=detector.get_mergify_config_path,
     help="Path to YAML config file.",
 )