Use github.com/saracen/walker for file walk operations

In some local tests w/ a slowed down filesystem, this massively cut down
on the time to clean up a repository by ~3x, bringing a total 'publish
update' time from ~16s to ~13s.

Signed-off-by: Ryan Gonzalez <ryan.gonzalez@collabora.com>

files/public.go

@@ -5,11 +5,14 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"sort"
 	"strings"
+	"sync"
 	"syscall"
 
 	"github.com/aptly-dev/aptly/aptly"
 	"github.com/aptly-dev/aptly/utils"
+	"github.com/saracen/walker"
 )
 
 // PublishedStorage abstract file system with public dirs (published repos)
@@ -232,12 +235,12 @@ func (storage *PublishedStorage) LinkFromPool(publishedPrefix, publishedRelPath,
 func (storage *PublishedStorage) Filelist(prefix string) ([]string, error) {
 	root := filepath.Join(storage.rootPath, prefix)
 	result := []string{}
+	resultLock := &sync.Mutex{}
 
-	err := filepath.Walk(root, func(path string, info os.FileInfo, err error) error {
-		if err != nil {
-			return err
-		}
+	err := walker.Walk(root, func(path string, info os.FileInfo) error {
 		if !info.IsDir() {
+			resultLock.Lock()
+			defer resultLock.Unlock()
 			result = append(result, path[len(root)+1:])
 		}
 		return nil
@@ -248,6 +251,7 @@ func (storage *PublishedStorage) Filelist(prefix string) ([]string, error) {
 		return []string{}, nil
 	}
 
+	sort.Strings(result)
 	return result, err
 }