refactor(downloader): take &self across the downloader hierarchy

Concurrent package operations call into the same downloader instances
through Rc<RefCell<dyn DownloaderInterface>>; with &mut self methods
every call holds a RefMut across its awaits, which panics with
'already mutably borrowed' the moment two operations overlap. This is
groundwork for fanning out InstallationManager's download/install
loops (same rework HttpDownloader/CurlDownloader already got).

- DownloaderInterface/ChangeReportInterface/ArchiveDownloader/
  VcsDownloader methods now take &self; as_change_report_interface
  returns &dyn instead of &mut dyn.
- Implementors move their genuinely mutable state behind cells:
  FileDownloader.additional_cleanup_paths, the archive downloaders'
  cleanup_executed, ZipDownloader.zip_archive_object,
  VcsDownloaderBase.has_cleaned_changes, GitDownloader's stash/discard/
  cache maps and GitUtil, SvnDownloader.cache_credentials,
  PerforceDownloader.perforce. FileDownloader.io gains a RefCell layer
  so get_local_changes can keep PHP's NullIO swap under &self.
- ProcessExecutor::execute_async now returns a future that captures
  everything up front instead of borrowing the executor, and call
  sites build the future before awaiting, so no borrow on the shared
  executor is held while a subprocess runs.
- Filesystem::remove_directory_async becomes remove_directory_async_via
  taking the Rc handle: the Filesystem is only borrowed for the sync
  head/tail, never across the rm subprocess await (sync borrow_mut
  users like rename/ensure_directory_exists would otherwise collide).
- DownloadManager async call sites hold shared borrows only.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

1 files changed, 5 insertions, 5 deletions

diff --git a/crates/shirabe/tests/downloader/file_downloader_test.rs b/crates/shirabe/tests/downloader/file_downloader_test.rs
index a9af69ed..451b792e 100644
--- a/crates/shirabe/tests/downloader/file_downloader_test.rs
+++ b/crates/shirabe/tests/downloader/file_downloader_test.rs
@@ -79,7 +79,7 @@ fn get_downloader(
 fn test_download_for_package_without_dist_reference() {
     let package = get_package("dummy/pkg", "1.0.0");
 
-    let (mut downloader, _http_downloader, _guard) = get_downloader(None, None);
+    let (downloader, _http_downloader, _guard) = get_downloader(None, None);
     let result = run(downloader.download(package, "/path", None, true));
 
     let e = result.expect_err("expected InvalidArgumentException");
@@ -101,7 +101,7 @@ fn test_download_to_existing_file() {
     std::fs::write(&path, b"").unwrap();
     let path = path.to_string_lossy().into_owned();
 
-    let (mut downloader, _http_downloader, _guard) = get_downloader(None, None);
+    let (downloader, _http_downloader, _guard) = get_downloader(None, None);
 
     let result = run(downloader.download(package, &path, None, true));
 
@@ -154,7 +154,7 @@ fn test_download_but_file_is_unsaved() {
     );
     let config = get_config(config_options);
 
-    let (mut downloader, http_downloader, _guard) = get_downloader(None, Some(config));
+    let (downloader, http_downloader, _guard) = get_downloader(None, Some(config));
 
     let mut loop_ = Loop::new(http_downloader, None);
     let promise = Box::pin(async {
@@ -272,7 +272,7 @@ fn test_download_file_with_invalid_checksum() {
 
     // The PHP test injects a Filesystem mock so cleanup is a no-op; a real Filesystem behaves the
     // same here since nothing under the temp dir needs preserving.
-    let (mut downloader, http_downloader, _guard) = get_downloader(None, Some(config));
+    let (downloader, http_downloader, _guard) = get_downloader(None, Some(config));
 
     // make sure the file expected to be downloaded is on disk already
     let dl_file = downloader.__get_file_name(package.clone(), &path);
@@ -350,7 +350,7 @@ fn test_downgrade_shows_appropriate_message() {
     );
 
     let io: std::rc::Rc<std::cell::RefCell<dyn IOInterface>> = io_mock.clone();
-    let mut downloader = FileDownloader::new(
+    let downloader = FileDownloader::new(
         io,
         config,
         http_downloader.clone(),