refactor: move pkg/ to internal/ and update imports

Restructure project by relocating package contents from pkg/ to internal/ to better reflect internal-only usage. This commit is initial step to prepare project for public api

internal/build/utils_internal_test.go

@@ -0,0 +1,47 @@
+// ALR - Any Linux Repository
+// Copyright (C) 2025 The ALR Authors
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package build
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRemoveDuplicatesSources(t *testing.T) {
+	type testCase struct {
+		Name         string
+		Sources      []string
+		Checksums    []string
+		NewSources   []string
+		NewChecksums []string
+	}
+
+	for _, tc := range []testCase{{
+		Name:         "prefer non-skip values",
+		Sources:      []string{"a", "b", "c", "a"},
+		Checksums:    []string{"skip", "skip", "skip", "1"},
+		NewSources:   []string{"a", "b", "c"},
+		NewChecksums: []string{"1", "skip", "skip"},
+	}} {
+		t.Run(tc.Name, func(t *testing.T) {
+			s, c := removeDuplicatesSources(tc.Sources, tc.Checksums)
+			assert.Equal(t, s, tc.NewSources)
+			assert.Equal(t, c, tc.NewChecksums)
+		})
+	}
+}