stats: Convert `GetPackfiles()` to use `os.ReadDir()`

Go 1.15 has deprecated the `ioutil` package and made replacements
available in the `io` or `os` packages. While we have already migrated
most callsites away, one notable omission was `ioutil.ReadDir()` as this
function doesn't have an exact replacement: the new `os.ReadDir()`
function does not stat all directory entries anymore.

Refactor `stats.GetPackfiles()` to use the new function and manually
stat the packfiles at callsites as required.

3 files changed, 36 insertions, 18 deletions

diff --git a/internal/git/stats/profile.go b/internal/git/stats/profile.go
index 68d4e0991..85c4015f8 100644
--- a/internal/git/stats/profile.go
+++ b/internal/git/stats/profile.go
@@ -1,10 +1,9 @@
 package stats
 
-//nolint:depguard
 import (
 	"context"
 	"errors"
-	"io/ioutil"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -34,13 +33,13 @@ func PackfilesCount(repoPath string) (int, error) {
 }
 
 // GetPackfiles returns the FileInfo of packfiles inside a repository.
-func GetPackfiles(repoPath string) ([]os.FileInfo, error) {
-	files, err := ioutil.ReadDir(filepath.Join(repoPath, "objects/pack/"))
+func GetPackfiles(repoPath string) ([]fs.DirEntry, error) {
+	files, err := os.ReadDir(filepath.Join(repoPath, "objects/pack/"))
 	if err != nil {
 		return nil, err
 	}
 
-	var packFiles []os.FileInfo
+	var packFiles []fs.DirEntry
 	for _, f := range files {
 		if filepath.Ext(f.Name()) == ".pack" {
 			packFiles = append(packFiles, f)
diff --git a/internal/gitaly/service/repository/midx.go b/internal/gitaly/service/repository/midx.go
index 7691c0680..85c0f8809 100644
--- a/internal/gitaly/service/repository/midx.go
+++ b/internal/gitaly/service/repository/midx.go
@@ -2,7 +2,9 @@ package repository
 
 import (
 	"context"
+	"errors"
 	"fmt"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -209,28 +211,39 @@ func (s *server) midxRepack(ctx context.Context, repo repository.GitRepo) error
 // Reference:
 // - https://public-inbox.org/git/f3b25a9927fe560b764850ea880a71932ec2af32.1598380599.git.gitgitgadget@gmail.com/
 func calculateBatchSize(repoPath string) (int64, error) {
-	files, err := stats.GetPackfiles(repoPath)
+	packfiles, err := stats.GetPackfiles(repoPath)
 	if err != nil {
 		return 0, err
 	}
 
 	// In case of 2 or less packs,
 	// batch size should be 0 for a full repack
-	if len(files) <= 2 {
+	if len(packfiles) <= 2 {
 		return 0, nil
 	}
 
 	var biggestSize int64
 	var secondBiggestSize int64
-	for _, f := range files {
-		if f.Size() > biggestSize {
+	for _, packfile := range packfiles {
+		info, err := packfile.Info()
+		if err != nil {
+			// It's fine if the entry has disappeared meanwhile, we just don't account
+			// for its size.
+			if errors.Is(err, fs.ErrNotExist) {
+				continue
+			}
+
+			return 0, fmt.Errorf("statting packfile: %w", err)
+		}
+
+		if info.Size() > biggestSize {
 			secondBiggestSize = biggestSize
-			biggestSize = f.Size()
+			biggestSize = info.Size()
 			continue
 		}
 
-		if f.Size() > secondBiggestSize {
-			secondBiggestSize = f.Size()
+		if info.Size() > secondBiggestSize {
+			secondBiggestSize = info.Size()
 		}
 	}
 
diff --git a/internal/gitaly/service/repository/midx_test.go b/internal/gitaly/service/repository/midx_test.go
index ea358bf36..5057fbd37 100644
--- a/internal/gitaly/service/repository/midx_test.go
+++ b/internal/gitaly/service/repository/midx_test.go
@@ -5,6 +5,7 @@ package repository
 import (
 	"context"
 	"fmt"
+	"io/fs"
 	"os"
 	"path/filepath"
 	"testing"
@@ -111,8 +112,8 @@ func TestMidxRepack(t *testing.T) {
 		"At least 1 pack file should have been created",
 	)
 
-	newPackFile := findNewestPackFile(t, repoPath)
-	assert.True(t, newPackFile.ModTime().After(time.Time{}))
+	_, newPackFileInfo := findNewestPackFile(t, repoPath)
+	assert.True(t, newPackFileInfo.ModTime().After(time.Time{}))
 }
 
 func TestMidxRepack_transactional(t *testing.T) {
@@ -214,21 +215,26 @@ func TestMidxRepackExpire(t *testing.T) {
 }
 
 // findNewestPackFile returns the latest created pack file in repo's odb
-func findNewestPackFile(t *testing.T, repoPath string) os.FileInfo {
+func findNewestPackFile(t *testing.T, repoPath string) (fs.DirEntry, fs.FileInfo) {
 	t.Helper()
 
 	files, err := stats.GetPackfiles(repoPath)
 	require.NoError(t, err)
 
-	var newestPack os.FileInfo
+	var newestPack fs.DirEntry
+	var newestPackInfo fs.FileInfo
 	for _, f := range files {
-		if newestPack == nil || f.ModTime().After(newestPack.ModTime()) {
+		info, err := f.Info()
+		require.NoError(t, err)
+
+		if newestPack == nil || info.ModTime().After(newestPackInfo.ModTime()) {
 			newestPack = f
+			newestPackInfo = info
 		}
 	}
 	require.NotNil(t, newestPack)
 
-	return newestPack
+	return newestPack, newestPackInfo
 }
 
 // addPackFiles creates some packfiles by