s3: call s3.ListFiles only on publish path in LinkFromPool

instead of caching the whole s3 bucket, cache only the pool path. this
requires an additional parameter, and since this is an interface, all
implementations need to follow. might help in other backends too.

closes #1181

aptly/interfaces.go

@@ -70,7 +70,7 @@ type PublishedStorage interface {
 	// Remove removes single file under public path
 	Remove(path string) error
 	// LinkFromPool links package file from pool to dist's pool location
-	LinkFromPool(publishedDirectory, fileName string, sourcePool PackagePool, sourcePath string, sourceChecksums utils.ChecksumInfo, force bool) error
+	LinkFromPool(prefix string, path string, fileName string, sourcePool PackagePool, sourcePath string, sourceChecksums utils.ChecksumInfo, force bool) error
 	// Filelist returns list of files under prefix
 	Filelist(prefix string) ([]string, error)
 	// RenameFile renames (moves) file

azure/public.go

@@ -179,9 +179,10 @@ func (storage *PublishedStorage) Remove(path string) error {
 // sourcePath is filepath to package file in package pool
 //
 // LinkFromPool returns relative path for the published file to be included in package index
-func (storage *PublishedStorage) LinkFromPool(publishedDirectory, fileName string, sourcePool aptly.PackagePool,
+func (storage *PublishedStorage) LinkFromPool(prefix string, path string, fileName string, sourcePool aptly.PackagePool,
 	sourcePath string, sourceChecksums utils.ChecksumInfo, force bool) error {
 
+	publishedDirectory := filepath.Join(prefix, path)
 	relPath := filepath.Join(publishedDirectory, fileName)
 	poolPath := filepath.Join(storage.prefix, relPath)
 

deb/package.go

@@ -621,9 +621,7 @@ func (p *Package) LinkFromPool(publishedStorage aptly.PublishedStorage, packageP
 			return err
 		}
 
-		publishedDirectory := filepath.Join(prefix, relPath)
-
-		err = publishedStorage.LinkFromPool(publishedDirectory, f.Filename, packagePool, sourcePoolPath, f.Checksums, force)
+		err = publishedStorage.LinkFromPool(prefix, relPath, f.Filename, packagePool, sourcePoolPath, f.Checksums, force)
 		if err != nil {
 			return err
 		}

files/public.go

@@ -123,9 +123,10 @@ func (storage *PublishedStorage) RemoveDirs(path string, progress aptly.Progress
 // sourcePath is a relative path to package file in package pool
 //
 // LinkFromPool returns relative path for the published file to be included in package index
-func (storage *PublishedStorage) LinkFromPool(publishedDirectory, fileName string, sourcePool aptly.PackagePool,
+func (storage *PublishedStorage) LinkFromPool(prefix string, path string, fileName string, sourcePool aptly.PackagePool,
 	sourcePath string, sourceChecksums utils.ChecksumInfo, force bool) error {
 
+        publishedDirectory := filepath.Join(prefix, path)
 	baseName := filepath.Base(fileName)
 	poolPath := filepath.Join(storage.rootPath, publishedDirectory, filepath.Dir(fileName))
 

s3/public.go

@@ -310,14 +310,15 @@ func (storage *PublishedStorage) RemoveDirs(path string, _ aptly.Progress) error
 // sourcePath is filepath to package file in package pool
 //
 // LinkFromPool returns relative path for the published file to be included in package index
-func (storage *PublishedStorage) LinkFromPool(publishedDirectory, fileName string, sourcePool aptly.PackagePool,
+func (storage *PublishedStorage) LinkFromPool(prefix string, path string, fileName string, sourcePool aptly.PackagePool,
 	sourcePath string, sourceChecksums utils.ChecksumInfo, force bool) error {
 
+        publishedDirectory := filepath.Join(prefix, path)
 	relPath := filepath.Join(publishedDirectory, fileName)
 	poolPath := filepath.Join(storage.prefix, relPath)
 
 	if storage.pathCache == nil {
-		paths, md5s, err := storage.internalFilelist("", true)
+		paths, md5s, err := storage.internalFilelist(filepath.Join(storage.prefix, prefix, "pool"), true)
 		if err != nil {
 			return errors.Wrap(err, "error caching paths under prefix")
 		}

swift/public.go

@@ -193,9 +193,10 @@ func (storage *PublishedStorage) RemoveDirs(path string, _ aptly.Progress) error
 // sourcePath is filepath to package file in package pool
 //
 // LinkFromPool returns relative path for the published file to be included in package index
-func (storage *PublishedStorage) LinkFromPool(publishedDirectory, fileName string, sourcePool aptly.PackagePool,
+func (storage *PublishedStorage) LinkFromPool(prefix string, path string, fileName string, sourcePool aptly.PackagePool,
 	sourcePath string, sourceChecksums utils.ChecksumInfo, force bool) error {
 
+        publishedDirectory := filepath.Join(prefix, path)
 	relPath := filepath.Join(publishedDirectory, fileName)
 	poolPath := filepath.Join(storage.prefix, relPath)