Make GetMaintainerReleaseNotesAction git Process calls injectable to eliminate tmp dir in tests

[mglaman]

Context

GetMaintainerReleaseNotesActionTest currently creates a real temporary git repository in setUpBeforeClass() and deletes it in tearDownAfterClass(). This is needed because the action runs two git subprocesses directly via Process:

• git log (to get commit history between refs)
• git config --get remote.origin.url (to determine the project name)

These are real subprocess calls that require a real filesystem path — vfs:// paths from vfsstream are not usable by external processes.

Proposed fix

Make the git runner injectable via a \Closure, similar to how GetMaintainerIssuesAction accepts a $feedLoader closure:

public function __construct(
    private readonly Client $client,
    private readonly ?\Closure $processRunner = null,
) {}

The default implementation runs a real Process; tests inject a closure returning a mock result with pre-canned git log output and remote URL. This eliminates the need for a real temp directory and makes the tests fully in-process.

Related

• Part of Action/Result refactor milestone Refactor Commands to Action/Result Pattern for Multi-Channel Support #270
• GetMaintainerIssuesAction already uses this pattern for its feed loader