fix(mount): handle snapshot root path

subcommands/mount/mount.go

@@ -40,6 +40,8 @@ type Mount struct {
 	SnapshotPath string
 }
 
+const snapshotRootPath = "/"
+
 func init() {
 	subcommands.Register(func() subcommands.Subcommand { return &Mount{} }, 0, "mount")
 }
@@ -81,7 +83,7 @@ func (cmd *Mount) Execute(ctx *appcontext.AppContext, repo *repository.Repositor
 			return 1, err
 		}
 
-		subFS, err := fs.Sub(pvfs, path[1:])
+		subFS, err := snapshotSubFS(pvfs, path)
 		if err != nil {
 			return 1, err
 		}
@@ -93,3 +95,10 @@ func (cmd *Mount) Execute(ctx *appcontext.AppContext, repo *repository.Repositor
 	}
 	return fuse.ExecuteFUSE(ctx, repo, cmd.Mountpoint, cmd.LocateOptions, chrootFS, cmd.AllowOthers)
 }
+
+func snapshotSubFS(snapshotFS fs.FS, snapshotPath string) (fs.FS, error) {
+	if snapshotPath == snapshotRootPath {
+		return snapshotFS, nil
+	}
+	return fs.Sub(snapshotFS, strings.TrimPrefix(snapshotPath, snapshotRootPath))
+}

subcommands/mount/mount_parse_test.go

@@ -2,14 +2,21 @@ package mount
 
 import (
 	"bytes"
+	"io/fs"
 	"testing"
+	"testing/fstest"
 
 	_ "github.com/PlakarKorp/integrations/fs/exporter"
-	ptesting "github.com/PlakarKorp/plakar/testing"
 	"github.com/PlakarKorp/plakar/subcommands"
+	ptesting "github.com/PlakarKorp/plakar/testing"
 	"github.com/stretchr/testify/require"
 )
 
+const (
+	snapshotSubFSTestFile    = "a.txt"
+	snapshotSubFSTestContent = "x"
+)
+
 func TestMountRegisteredFactory(t *testing.T) {
 	cmd, _, _ := subcommands.Lookup([]string{"mount"})
 	require.NotNil(t, cmd)
@@ -46,6 +53,19 @@ func TestMountParseAllowOthers(t *testing.T) {
 	require.True(t, cmd.AllowOthers)
 }
 
+func TestSnapshotSubFSRootPathUsesSnapshotRoot(t *testing.T) {
+	snapshotFS := fstest.MapFS{
+		snapshotSubFSTestFile: &fstest.MapFile{Data: []byte(snapshotSubFSTestContent)},
+	}
+
+	subFS, err := snapshotSubFS(snapshotFS, snapshotRootPath)
+	require.NoError(t, err)
+
+	data, err := fs.ReadFile(subFS, snapshotSubFSTestFile)
+	require.NoError(t, err)
+	require.Equal(t, []byte(snapshotSubFSTestContent), data)
+}
+
 func TestMountExecuteBadSnapshot(t *testing.T) {
 	// A snapshot path that resolves to nothing fails before any mount is
 	// attempted (so this is safe on all platforms, FUSE never engages).