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, 20 insertions, 26 deletions

diff --git a/crates/shirabe/src/downloader/svn_downloader.rs b/crates/shirabe/src/downloader/svn_downloader.rs
index b2dd7f58..576a2676 100644
--- a/crates/shirabe/src/downloader/svn_downloader.rs
+++ b/crates/shirabe/src/downloader/svn_downloader.rs
@@ -21,7 +21,7 @@ use shirabe_php_shim::{PhpMixed, RuntimeException, is_dir, php_regex, version_co
 #[derive(Debug)]
 pub struct SvnDownloader {
     inner: VcsDownloaderBase,
-    pub(crate) cache_credentials: bool,
+    pub(crate) cache_credentials: std::cell::Cell<bool>,
 }
 
 impl SvnDownloader {
@@ -33,7 +33,7 @@ impl SvnDownloader {
     ) -> Self {
         Self {
             inner: VcsDownloaderBase::new(io, config, Some(process), Some(fs)),
-            cache_credentials: true,
+            cache_credentials: std::cell::Cell::new(true),
         }
     }
 
@@ -52,7 +52,7 @@ impl SvnDownloader {
             self.inner.config.clone(),
             Some(self.inner.process.clone()),
         );
-        util.set_cache_credentials(self.cache_credentials);
+        util.set_cache_credentials(self.cache_credentials.get());
         util.execute(command, url, cwd, path, self.inner.io.is_verbose())
             .map_err(|e| {
                 anyhow::anyhow!(
@@ -87,7 +87,7 @@ impl SvnDownloader {
     /// The default `VcsDownloader::clean_changes()` behavior: fail if the working copy has
     /// local changes.
     fn fail_on_local_changes(
-        &mut self,
+        &self,
         package: PackageInterfaceHandle,
         path: &str,
     ) -> anyhow::Result<()> {
@@ -120,16 +120,12 @@ impl VcsDownloader for SvnDownloader {
         &self.inner.filesystem
     }
 
-    fn has_cleaned_changes(&self) -> &IndexMap<String, bool> {
+    fn has_cleaned_changes(&self) -> &std::cell::RefCell<IndexMap<String, bool>> {
         &self.inner.has_cleaned_changes
     }
 
-    fn has_cleaned_changes_mut(&mut self) -> &mut IndexMap<String, bool> {
-        &mut self.inner.has_cleaned_changes
-    }
-
     async fn do_download(
-        &mut self,
+        &self,
         _package: PackageInterfaceHandle,
         _path: &str,
         url: &str,
@@ -154,7 +150,7 @@ impl VcsDownloader for SvnDownloader {
     }
 
     async fn do_install(
-        &mut self,
+        &self,
         package: PackageInterfaceHandle,
         path: &str,
         url: &str,
@@ -173,7 +169,7 @@ impl VcsDownloader for SvnDownloader {
                             .get("svn-cache-credentials")
                             .and_then(|v| v.as_bool())
                     {
-                        self.cache_credentials = val;
+                        self.cache_credentials.set(val);
                     }
                 }
             }
@@ -200,7 +196,7 @@ impl VcsDownloader for SvnDownloader {
     }
 
     async fn do_update(
-        &mut self,
+        &self,
         _initial: PackageInterfaceHandle,
         target: PackageInterfaceHandle,
         path: &str,
@@ -251,7 +247,7 @@ impl VcsDownloader for SvnDownloader {
     }
 
     async fn clean_changes(
-        &mut self,
+        &self,
         package: PackageInterfaceHandle,
         path: &str,
         update: bool,
@@ -359,7 +355,7 @@ impl VcsDownloader for SvnDownloader {
     }
 
     fn get_commit_logs(
-        &mut self,
+        &self,
         from_reference: &str,
         to_reference: &str,
         path: &str,
@@ -428,7 +424,7 @@ impl VcsDownloader for SvnDownloader {
                 self.inner.config.clone(),
                 Some(self.inner.process.clone()),
             );
-            util.set_cache_credentials(self.cache_credentials);
+            util.set_cache_credentials(self.cache_credentials.get());
             util.execute_local(command.clone(), path, None, self.inner.io.is_verbose())
                 .map_err(|e| {
                     RuntimeException {
@@ -452,7 +448,7 @@ impl VcsDownloader for SvnDownloader {
 
 impl ChangeReportInterface for SvnDownloader {
     fn get_local_changes(
-        &mut self,
+        &self,
         _package: PackageInterfaceHandle,
         path: &str,
     ) -> anyhow::Result<Option<String>> {
@@ -489,9 +485,7 @@ impl DownloaderInterface for SvnDownloader {
         <Self as VcsDownloader>::get_installation_source(self)
     }
 
-    fn as_change_report_interface(
-        &mut self,
-    ) -> Option<&mut dyn crate::downloader::ChangeReportInterface> {
+    fn as_change_report_interface(&self) -> Option<&dyn crate::downloader::ChangeReportInterface> {
         Some(self)
     }
 
@@ -502,7 +496,7 @@ impl DownloaderInterface for SvnDownloader {
     }
 
     async fn download(
-        &mut self,
+        &self,
         package: PackageInterfaceHandle,
         path: &str,
         prev_package: Option<PackageInterfaceHandle>,
@@ -512,7 +506,7 @@ impl DownloaderInterface for SvnDownloader {
     }
 
     async fn prepare(
-        &mut self,
+        &self,
         r#type: &str,
         package: PackageInterfaceHandle,
         path: &str,
@@ -522,7 +516,7 @@ impl DownloaderInterface for SvnDownloader {
     }
 
     async fn install(
-        &mut self,
+        &self,
         package: PackageInterfaceHandle,
         path: &str,
         _output: bool,
@@ -531,7 +525,7 @@ impl DownloaderInterface for SvnDownloader {
     }
 
     async fn update(
-        &mut self,
+        &self,
         initial: PackageInterfaceHandle,
         target: PackageInterfaceHandle,
         path: &str,
@@ -540,7 +534,7 @@ impl DownloaderInterface for SvnDownloader {
     }
 
     async fn remove(
-        &mut self,
+        &self,
         package: PackageInterfaceHandle,
         path: &str,
         _output: bool,
@@ -549,7 +543,7 @@ impl DownloaderInterface for SvnDownloader {
     }
 
     async fn cleanup(
-        &mut self,
+        &self,
         r#type: &str,
         package: PackageInterfaceHandle,
         path: &str,