Fix bug with PoolPath field being overwritten on mirror update

While updating mirror, if package file is already in pool path,
field `PoolPath` was left as empty which results in package file
being unavailable later on while publishing.

deb/package.go

@@ -629,14 +629,15 @@ type PackageDownloadTask struct {
 func (p *Package) DownloadList(packagePool aptly.PackagePool, checksumStorage aptly.ChecksumStorage) (result []PackageDownloadTask, err error) {
 	result = make([]PackageDownloadTask, 0, 1)
 
-	for idx, f := range p.Files() {
-		verified, err := f.Verify(packagePool, checksumStorage)
+	files := p.Files()
+	for idx := range files {
+		verified, err := files[idx].Verify(packagePool, checksumStorage)
 		if err != nil {
 			return nil, err
 		}
 
 		if !verified {
-			result = append(result, PackageDownloadTask{File: &p.Files()[idx]})
+			result = append(result, PackageDownloadTask{File: &files[idx]})
 		}
 	}
 

deb/package_files.go

@@ -27,7 +27,12 @@ type PackageFile struct {
 
 // Verify that package file is present and correct
 func (f *PackageFile) Verify(packagePool aptly.PackagePool, checksumStorage aptly.ChecksumStorage) (bool, error) {
-	return packagePool.Verify(f.PoolPath, f.Filename, &f.Checksums, checksumStorage)
+	generatedPoolPath, exists, err := packagePool.Verify(f.PoolPath, f.Filename, &f.Checksums, checksumStorage)
+	if exists && err == nil {
+		f.PoolPath = generatedPoolPath
+	}
+
+	return exists, err
 }
 
 // GetPoolPath returns path to the file in the pool