feat(vcs): add mozart-vcs crate for VCS repository support

Implement VCS driver/downloader infrastructure mirroring Composer's VCS
subsystem. Includes drivers for GitHub, GitLab, Bitbucket, Forgejo, Git,
Hg, and SVN with API-based metadata resolution, plus source downloaders
for Git/Hg/SVN. Integrates into mozart-registry via vcs_bridge module to
scan VCS repositories and feed discovered packages into the SAT resolver.

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

1 files changed, 31 insertions, 0 deletions

diff --git a/crates/mozart-vcs/src/downloader/mod.rs b/crates/mozart-vcs/src/downloader/mod.rs
new file mode 100644
index 0000000..7186348
--- /dev/null
+++ b/crates/mozart-vcs/src/downloader/mod.rs
@@ -0,0 +1,31 @@
+pub mod git;
+pub mod hg;
+pub mod svn;
+
+use std::path::Path;
+
+use anyhow::Result;
+
+/// The VCS downloader interface.
+///
+/// Corresponds to Composer's `VcsDownloader` hierarchy.
+pub trait VcsDownloader {
+    /// Prepare for installation (e.g., sync mirror cache).
+    fn download(&self, url: &str, reference: &str, target: &Path) -> Result<()>;
+
+    /// Install (clone/checkout) the source to the target directory.
+    fn install(&self, url: &str, reference: &str, target: &Path) -> Result<()>;
+
+    /// Update the source at target to a new reference.
+    fn update(&self, url: &str, old_ref: &str, new_ref: &str, target: &Path) -> Result<()>;
+
+    /// Remove the source from the target directory.
+    fn remove(&self, target: &Path) -> Result<()>;
+
+    /// Detect local changes in the working copy.
+    /// Returns `None` if clean, `Some(diff)` if modified.
+    fn local_changes(&self, target: &Path) -> Result<Option<String>>;
+
+    /// Get commit log between two references.
+    fn commit_logs(&self, from: &str, to: &str, target: &Path) -> Result<String>;
+}