cache: Add detection code for old cache dirs

cmd/restic/global.go

@@ -353,13 +353,21 @@ func OpenRepository(opts GlobalOptions) (*repository.Repository, error) {
 		return s, nil
 	}
 
-	cache, err := cache.New(s.Config().ID, opts.CacheDir)
+	c, err := cache.New(s.Config().ID, opts.CacheDir)
 	if err != nil {
 		Warnf("unable to open cache: %v\n", err)
-	} else {
-		s.UseCache(cache)
+		return s, nil
 	}
 
+	oldCacheDirs, err := cache.Old(c.Base)
+	if err != nil {
+		Warnf("unable to find old cache directories: %v", err)
+	} else {
+		Verbosef("found %d old cache directories in %v remove them with 'restic cache --cleanup'\n",
+			len(oldCacheDirs), c.Base)
+	}
+
+	s.UseCache(c)
 	return s, nil
 }
 

internal/cache/cache.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"path/filepath"
 	"strconv"
+	"time"
 
 	"github.com/pkg/errors"
 	"github.com/restic/restic/internal/debug"
@@ -107,6 +108,11 @@ func New(id string, basedir string) (c *Cache, err error) {
 		return nil, errors.New("cache version is newer")
 	}
 
+	err = updateTimestamp(cachedir)
+	if err != nil {
+		return nil, err
+	}
+
 	// create the repo cache dir if it does not exist yet
 	if err = fs.MkdirAll(cachedir, dirMode); err != nil {
 		return nil, err
@@ -137,6 +143,53 @@ func New(id string, basedir string) (c *Cache, err error) {
 	return c, nil
 }
 
+// updateTimestamp sets the modification timestamp (mtime and atime) for the
+// directory d to the current time.
+func updateTimestamp(d string) error {
+	t := time.Now()
+	return fs.Chtimes(d, t, t)
+}
+
+const maxCacheAge = 30 * 24 * time.Hour
+
+// Old returns a list of cache directories with a modification time of more
+// than 30 days ago.
+func Old(basedir string) ([]string, error) {
+	var oldCacheDirs []string
+
+	f, err := fs.Open(basedir)
+	if err != nil {
+		return nil, err
+	}
+
+	entries, err := f.Readdir(-1)
+	if err != nil {
+		return nil, err
+	}
+
+	oldest := time.Now().Add(-maxCacheAge)
+	for _, fi := range entries {
+		if !fi.IsDir() {
+			continue
+		}
+
+		if !fi.ModTime().Before(oldest) {
+			continue
+		}
+
+		oldCacheDirs = append(oldCacheDirs, fi.Name())
+	}
+
+	err = f.Close()
+	if err != nil {
+		return nil, err
+	}
+
+	debug.Log("%d old cache dirs found", len(oldCacheDirs))
+
+	return oldCacheDirs, nil
+}
+
 // errNoSuchFile is returned when a file is not cached.
 type errNoSuchFile struct {
 	Type string

internal/fs/file.go

@@ -4,6 +4,7 @@ import (
 	"io"
 	"os"
 	"path/filepath"
+	"time"
 )
 
 // File is an open file on a file system.
@@ -120,3 +121,12 @@ func RemoveIfExists(filename string) error {
 	}
 	return err
 }
+
+// Chtimes changes the access and modification times of the named file,
+// similar to the Unix utime() or utimes() functions.
+//
+// The underlying filesystem may truncate or round the values to a less
+// precise time unit. If there is an error, it will be of type *PathError.
+func Chtimes(name string, atime time.Time, mtime time.Time) error {
+	return os.Chtimes(fixpath(name), atime, mtime)
+}