Resolve dependencies through the repositories the packages filter dropped

A partial build (`satis build satis.json web/ vendor/package`) narrows the
repository list down to the ones providing the requested packages. The
dependency pass then reused that narrowed list, so with
`require-dependencies` nothing the filtered package required could be
found -- packagist.org and every other repository had already been
dropped. Feed the dependency repository set the repositories the filter
removed, the same way the repository-URL filter already does.

Fixes #706

src/PackageSelection/PackageSelection.php

@@ -221,12 +221,17 @@ class PackageSelection
             }
         }
 
-        if ($this->hasFilterForPackages()) {
-            $repos = $this->filterPackages($repos);
+        $reposDroppedByPackagesFilter = [];
 
-            if (0 === count($repos)) {
+        if ($this->hasFilterForPackages()) {
+            $filteredRepos = $this->filterPackages($repos);
+
+            if (0 === count($filteredRepos)) {
                 throw new \InvalidArgumentException(sprintf('Could not find any repositories config with "name" matching your package(s) filter: %s', implode(', ', $this->packagesFilter)));
             }
+
+            $reposDroppedByPackagesFilter = array_filter($repos, static fn ($repo) => !in_array($repo, $filteredRepos, true));
+            $repos = $filteredRepos;
         }
 
         $repositorySet = new RepositorySet($this->minimumStability, $stabilityFlags);
@@ -253,6 +258,9 @@ class PackageSelection
                 );
             }
 
+            // the packages filter picks what to request, not who may answer a dependency
+            $this->addRepositories($repositorySet, $reposDroppedByPackagesFilter);
+
             // additional repositories for dependencies
             if (!$this->hasRepositoriesFilter() || true !== $this->repositoryFilterDep) {
                 $this->addRepositories($repositorySet, $this->getDepRepos($composer));