fix(status): align with Composer's StatusCommand pipeline

Replace the dist-hash tree-diff implementation with Composer's VCS-level
status flow: three buckets (errors / unpushed_changes / vcs_version_changes)
populated via ChangeReportInterface / DvcsDownloaderInterface /
VcsCapableDownloaderInterface, and a bitfield exit code (1|2|4) instead
of always 1.

Supporting work:
- mozart-semver: add normalize_branch (VersionParser::normalizeBranch).
- mozart-vcs: extend VcsDownloader trait with unpushed_changes /
  vcs_reference; port GitDownloader::getUnpushedChanges (HEAD-ref
  discovery + git diff --name-status remote...branch + two-pass fetch);
  fix git status invocation to use --untracked-files=no (Composer parity);
  add hasMetadataRepository preconditions to git/hg/svn local_changes;
  port VersionGuesser (git/hg/svn dispatch — Fossil omitted, feature
  branch detection runs sequentially instead of via async promises).
- mozart-core: extend LocalPackage with pretty_version, package_type,
  installation_source, source, dist, extra; add InstallationSource and
  PackageReference. factory.rs reads them from installed.json.
- mozart-registry: new download_manager mirroring
  DownloadManager::getDownloaderForPackage.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

2 files changed, 141 insertions, 0 deletions

diff --git a/crates/mozart-registry/src/download_manager.rs b/crates/mozart-registry/src/download_manager.rs
new file mode 100644
index 0000000..3e05517
--- /dev/null
+++ b/crates/mozart-registry/src/download_manager.rs
@@ -0,0 +1,140 @@
+//! `DownloadManager` — pick the right [`VcsDownloader`] for a given
+//! [`LocalPackage`]. Mirrors `Composer\Downloader\DownloadManager`.
+
+use std::path::PathBuf;
+
+use mozart_core::composer::{InstallationSource, LocalPackage};
+use mozart_vcs::downloader::VcsDownloader;
+use mozart_vcs::downloader::git::GitDownloader;
+use mozart_vcs::downloader::hg::HgDownloader;
+use mozart_vcs::downloader::svn::SvnDownloader;
+use mozart_vcs::process::ProcessExecutor;
+use mozart_vcs::util::git::GitUtil;
+use mozart_vcs::util::hg::HgUtil;
+use mozart_vcs::util::svn::SvnUtil;
+
+/// Selects a `VcsDownloader` for a package based on its installation source
+/// and source type. Mirrors `DownloadManager::getDownloaderForPackage`:
+///
+/// - `metapackage` → `None`.
+/// - `installation-source: dist` → `None` (Composer would return a
+///   `FileDownloader`-family object that does not implement
+///   `ChangeReportInterface` / `DvcsDownloaderInterface`, so the status
+///   command's `instanceof` checks all become no-ops; returning `None`
+///   directly is the equivalent in our trait-object world).
+/// - `installation-source: source` → the matching VCS downloader by
+///   `source.type` (`git` / `hg` / `svn`).
+pub struct DownloadManager {
+    git_cache_dir: PathBuf,
+}
+
+impl DownloadManager {
+    /// `git_cache_dir`: where `GitUtil` should keep mirror clones (e.g.
+    /// `<vendor>/.cache/git`).
+    pub fn new(git_cache_dir: PathBuf) -> Self {
+        Self { git_cache_dir }
+    }
+
+    pub fn for_package(&self, package: &LocalPackage) -> Option<Box<dyn VcsDownloader>> {
+        if package.package_type() == Some("metapackage") {
+            return None;
+        }
+        match package.installation_source()? {
+            InstallationSource::Dist => None,
+            InstallationSource::Source => {
+                let kind = package.source()?.kind.as_str();
+                match kind {
+                    "git" => {
+                        let git_util =
+                            GitUtil::new(ProcessExecutor::new(), self.git_cache_dir.clone());
+                        Some(Box::new(GitDownloader::new(git_util)))
+                    }
+                    "hg" => {
+                        let hg_util = HgUtil::new(ProcessExecutor::new());
+                        Some(Box::new(HgDownloader::new(hg_util)))
+                    }
+                    "svn" => {
+                        let svn_util = SvnUtil::new(ProcessExecutor::new());
+                        Some(Box::new(SvnDownloader::new(svn_util)))
+                    }
+                    _ => None,
+                }
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use mozart_core::composer::PackageReference;
+    use serde_json::Value;
+
+    fn pkg(
+        installation_source: Option<InstallationSource>,
+        source_kind: Option<&str>,
+    ) -> LocalPackage {
+        let source = source_kind.map(|kind| PackageReference {
+            kind: kind.to_string(),
+            url: "https://example/repo".into(),
+            reference: Some("abc123".into()),
+            shasum: None,
+        });
+        LocalPackage::new(
+            "vendor/pkg".into(),
+            "1.0.0".into(),
+            None,
+            Some("library".into()),
+            installation_source,
+            source,
+            None,
+            Value::Null,
+        )
+    }
+
+    #[test]
+    fn metapackage_returns_none() {
+        let dm = DownloadManager::new(PathBuf::from("/tmp/mz-test-cache"));
+        let mut p = pkg(Some(InstallationSource::Source), Some("git"));
+        // override type
+        p = LocalPackage::new(
+            "vendor/pkg".into(),
+            "1.0.0".into(),
+            None,
+            Some("metapackage".into()),
+            p.installation_source(),
+            p.source().cloned(),
+            None,
+            Value::Null,
+        );
+        assert!(dm.for_package(&p).is_none());
+    }
+
+    #[test]
+    fn dist_install_returns_none() {
+        let dm = DownloadManager::new(PathBuf::from("/tmp/mz-test-cache"));
+        let p = pkg(Some(InstallationSource::Dist), Some("git"));
+        assert!(dm.for_package(&p).is_none());
+    }
+
+    #[test]
+    fn source_install_with_git_returns_some() {
+        let dm = DownloadManager::new(PathBuf::from("/tmp/mz-test-cache"));
+        let p = pkg(Some(InstallationSource::Source), Some("git"));
+        assert!(dm.for_package(&p).is_some());
+    }
+
+    #[test]
+    fn unknown_source_kind_returns_none() {
+        let dm = DownloadManager::new(PathBuf::from("/tmp/mz-test-cache"));
+        let p = pkg(Some(InstallationSource::Source), Some("perforce"));
+        assert!(dm.for_package(&p).is_none());
+    }
+
+    #[test]
+    fn missing_installation_source_returns_none() {
+        let dm = DownloadManager::new(PathBuf::from("/tmp/mz-test-cache"));
+        let p = pkg(None, Some("git"));
+        assert!(dm.for_package(&p).is_none());
+    }
+}
diff --git a/crates/mozart-registry/src/lib.rs b/crates/mozart-registry/src/lib.rs
index 36a12c6..9d72c36 100644
--- a/crates/mozart-registry/src/lib.rs
+++ b/crates/mozart-registry/src/lib.rs
@@ -1,6 +1,7 @@
 pub mod browse_repos;
 pub mod cache;
 pub mod composer_repo;
+pub mod download_manager;
 pub mod downloader;
 pub mod inline_package;
 pub mod installed;