Move attachment into models/repo/ (#17650)

* Move attachment into models/repo/

* Fix test

* Fix bug

models/repo_test.go

@@ -13,6 +13,7 @@ import (
 	"testing"
 
 	"code.gitea.io/gitea/models/db"
+	repo_model "code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/models/unit"
 	"code.gitea.io/gitea/models/unittest"
 	"code.gitea.io/gitea/modules/markup"
@@ -224,3 +225,30 @@ func TestRepoGetReviewerTeams(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Len(t, teams, 2)
 }
+
+func TestLinkedRepository(t *testing.T) {
+	assert.NoError(t, unittest.PrepareTestDatabase())
+	testCases := []struct {
+		name             string
+		attachID         int64
+		expectedRepo     *Repository
+		expectedUnitType unit.Type
+	}{
+		{"LinkedIssue", 1, &Repository{ID: 1}, unit.TypeIssues},
+		{"LinkedComment", 3, &Repository{ID: 1}, unit.TypePullRequests},
+		{"LinkedRelease", 9, &Repository{ID: 1}, unit.TypeReleases},
+		{"Notlinked", 10, nil, -1},
+	}
+	for _, tc := range testCases {
+		t.Run(tc.name, func(t *testing.T) {
+			attach, err := repo_model.GetAttachmentByID(tc.attachID)
+			assert.NoError(t, err)
+			repo, unitType, err := LinkedRepository(attach)
+			assert.NoError(t, err)
+			if tc.expectedRepo != nil {
+				assert.Equal(t, tc.expectedRepo.ID, repo.ID)
+			}
+			assert.Equal(t, tc.expectedUnitType, unitType)
+		})
+	}
+}