perf(package): hand out link maps behind Rc

PackageInterface::getRequires() and friends return the array of Link objects;
in PHP that is a copy-on-write array of object references, so a caller pays
nothing to look at it. The port returned IndexMap<String, Link> by value, so
every call deep-cloned the whole map, keys and constraints included. Pool
building calls these accessors once per package per candidate, which put
IndexMap::clone at 13.5% of `require laravel/laravel`.

Store the maps as Rc<IndexMap<String, Link>> and return a handle. Callers that
mutate the map clone it explicitly at the point of mutation, matching where PHP
would separate the array.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/crates/shirabe/src/util/package_sorter.rs b/crates/shirabe/src/util/package_sorter.rs
index 5687a339..9770375b 100644
--- a/crates/shirabe/src/util/package_sorter.rs
+++ b/crates/shirabe/src/util/package_sorter.rs
@@ -43,9 +43,14 @@ impl PackageSorter {
         let mut usage_list: IndexMap<String, Vec<String>> = IndexMap::new();
 
         for package in &packages {
-            let mut links: IndexMap<String, Link> = package.get_requires();
+            let mut links: IndexMap<String, Link> = (*package.get_requires()).clone();
             if let Some(root_package) = package.as_root() {
-                links.extend(root_package.get_dev_requires());
+                links.extend(
+                    root_package
+                        .get_dev_requires()
+                        .iter()
+                        .map(|(k, v)| (k.clone(), v.clone())),
+                );
             }
             for link in links.values() {
                 let target = link.get_target().to_string();