feat: add metapackage build support and fail-fast custom scripts

- add BuildType::Meta handling in builder and interactive spec output
- allow metapackage specs without sources and expose is_metapackage()
- avoid build deps in install planning for metapackages
- run custom non-function build.sh scripts with `sh -e` to stop on first failure
- add regression test for custom script fail-fast behavior
- apply small cleanup refactors (let-chains/iterator simplifications)

src/db/mod.rs

@@ -83,13 +83,13 @@ pub fn register_package(db_path: &Path, spec: &PackageSpec, destdir: &Path) -> R
             params![file],
             |row| row.get(0),
         );
-        if let Ok(owner) = owner_res {
-            if owner != spec.package.name {
-                if is_auto_removable_path(file) {
-                    auto_conflicts.push((file.clone(), owner));
-                } else {
-                    fatal_conflicts.push((file.clone(), owner));
-                }
+        if let Ok(owner) = owner_res
+            && owner != spec.package.name
+        {
+            if is_auto_removable_path(file) {
+                auto_conflicts.push((file.clone(), owner));
+            } else {
+                fatal_conflicts.push((file.clone(), owner));
             }
         }
     }

src/db/repo.rs

@@ -1019,11 +1019,11 @@ pub fn sync_mirrors(
                 .with_context(|| format!("Failed to fetch updates for {}", url))?;
 
             // Try to fast-forward HEAD to origin/HEAD by resetting to FETCH_HEAD if present
-            if let Ok(fetch_head) = repo.find_reference("FETCH_HEAD") {
-                if let Some(oid) = fetch_head.target() {
-                    let obj = repo.find_object(oid, None)?;
-                    repo.reset(&obj, ResetType::Hard, None)?;
-                }
+            if let Ok(fetch_head) = repo.find_reference("FETCH_HEAD")
+                && let Some(oid) = fetch_head.target()
+            {
+                let obj = repo.find_object(oid, None)?;
+                repo.reset(&obj, ResetType::Hard, None)?;
             }
         }
 
@@ -1055,7 +1055,7 @@ pub fn mirrors_status(
         return Ok(());
     }
 
-    for (name, _url) in mirrors {
+    for name in mirrors.keys() {
         let target = base.join(name);
         crate::log_info!("--- {} ---", name);
         if !target.exists() {
@@ -1080,11 +1080,11 @@ pub fn mirrors_status(
 
                 // Commit time (seconds since epoch) if available
                 let mut commit_time = String::new();
-                if let Some(oid) = oid {
-                    if let Ok(commit) = repo.find_commit(oid) {
-                        let t = commit.time().seconds();
-                        commit_time = format!("{}", t);
-                    }
+                if let Some(oid) = oid
+                    && let Ok(commit) = repo.find_commit(oid)
+                {
+                    let t = commit.time().seconds();
+                    commit_time = format!("{}", t);
                 }
 
                 // Dirty status