feat: add gc command and fix Docker-Content-Digest for Helm OCI

- Add nora gc --dry-run command for orphaned blob cleanup
- Fix Docker-Content-Digest header in blob upload response (enables Helm OCI push)
- Mark-and-sweep GC: list blobs, parse manifests, find/delete orphans

DevITWay

nora-registry/src/gc.rs

@@ -0,0 +1,118 @@
+//! Garbage Collection for orphaned blobs
+//!
+//! Mark-and-sweep approach:
+//! 1. List all blobs across registries
+//! 2. Parse all manifests to find referenced blobs
+//! 3. Blobs not referenced by any manifest = orphans
+//! 4. Delete orphans (with --dry-run support)
+
+use std::collections::HashSet;
+
+use tracing::info;
+
+use crate::storage::Storage;
+
+pub struct GcResult {
+    pub total_blobs: usize,
+    pub referenced_blobs: usize,
+    pub orphaned_blobs: usize,
+    pub deleted_blobs: usize,
+    pub orphan_keys: Vec<String>,
+}
+
+pub async fn run_gc(storage: &Storage, dry_run: bool) -> GcResult {
+    info!("Starting garbage collection (dry_run={})", dry_run);
+
+    // 1. Collect all blob keys
+    let all_blobs = collect_all_blobs(storage).await;
+    info!("Found {} total blobs", all_blobs.len());
+
+    // 2. Collect all referenced digests from manifests
+    let referenced = collect_referenced_digests(storage).await;
+    info!("Found {} referenced digests from manifests", referenced.len());
+
+    // 3. Find orphans
+    let mut orphan_keys: Vec<String> = Vec::new();
+    for key in &all_blobs {
+        if let Some(digest) = key.rsplit('/').next() {
+            if !referenced.contains(digest) {
+                orphan_keys.push(key.clone());
+            }
+        }
+    }
+
+    info!("Found {} orphaned blobs", orphan_keys.len());
+
+    let mut deleted = 0;
+    if !dry_run {
+        for key in &orphan_keys {
+            if storage.delete(key).await.is_ok() {
+                deleted += 1;
+                info!("Deleted: {}", key);
+            }
+        }
+        info!("Deleted {} orphaned blobs", deleted);
+    } else {
+        for key in &orphan_keys {
+            info!("[dry-run] Would delete: {}", key);
+        }
+    }
+
+    GcResult {
+        total_blobs: all_blobs.len(),
+        referenced_blobs: referenced.len(),
+        orphaned_blobs: orphan_keys.len(),
+        deleted_blobs: deleted,
+        orphan_keys,
+    }
+}
+
+async fn collect_all_blobs(storage: &Storage) -> Vec<String> {
+    let mut blobs = Vec::new();
+    let docker_blobs = storage.list("docker/").await;
+    for key in docker_blobs {
+        if key.contains("/blobs/") {
+            blobs.push(key);
+        }
+    }
+    blobs
+}
+
+async fn collect_referenced_digests(storage: &Storage) -> HashSet<String> {
+    let mut referenced = HashSet::new();
+
+    let all_keys = storage.list("docker/").await;
+    for key in &all_keys {
+        if !key.contains("/manifests/") || !key.ends_with(".json") || key.ends_with(".meta.json") {
+            continue;
+        }
+
+        if let Ok(data) = storage.get(key).await {
+            if let Ok(json) = serde_json::from_slice::<serde_json::Value>(&data) {
+                if let Some(config) = json.get("config") {
+                    if let Some(digest) = config.get("digest").and_then(|v| v.as_str()) {
+                        referenced.insert(digest.to_string());
+                    }
+                }
+
+                if let Some(layers) = json.get("layers").and_then(|v| v.as_array()) {
+                    for layer in layers {
+                        if let Some(digest) = layer.get("digest").and_then(|v| v.as_str()) {
+                            referenced.insert(digest.to_string());
+                        }
+                    }
+                }
+
+                if let Some(manifests) = json.get("manifests").and_then(|v| v.as_array()) {
+                    for m in manifests {
+                        if let Some(digest) = m.get("digest").and_then(|v| v.as_str()) {
+                            referenced.insert(digest.to_string());
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    referenced
+}