feat: upgrade existing filesystem

cmd/chisel/cmd_cut.go

@@ -11,6 +11,7 @@ import (
 	"github.com/canonical/chisel/internal/cache"
 	"github.com/canonical/chisel/internal/setup"
 	"github.com/canonical/chisel/internal/slicer"
+	"github.com/canonical/chisel/public/manifest"
 )
 
 var shortCutHelp = "Cut a tree with selected slices"
@@ -73,6 +74,24 @@ func (cmd *cmdCut) Execute(args []string) error {
 		}
 	}
 
+	mfest, err := slicer.SelectValidManifest(cmd.RootDir, release)
+	if err != nil {
+		return err
+	}
+	if mfest != nil {
+		err = mfest.IterateSlices("", func(slice *manifest.Slice) error {
+			sk, err := setup.ParseSliceKey(slice.Name)
+			if err != nil {
+				return err
+			}
+			sliceKeys = append(sliceKeys, sk)
+			return nil
+		})
+		if err != nil {
+			return err
+		}
+	}
+
 	selection, err := setup.Select(release, sliceKeys, cmd.Arch)
 	if err != nil {
 		return err
@@ -125,6 +144,7 @@ func (cmd *cmdCut) Execute(args []string) error {
 		Selection: selection,
 		Archives:  archives,
 		TargetDir: cmd.RootDir,
+		Manifest:  mfest,
 	})
 	return err
 }

internal/deb/extract_test.go

@@ -485,7 +485,7 @@ var extractTests = []extractTest{{
 			}},
 		},
 	},
-	error: `cannot extract from package "test-package": cannot create path /[a-z0-9\-\/]*/file outside of root /[a-z0-9\-\/]*`,
+	error: `cannot extract from package "test-package": cannot handle path /[a-z0-9\-\/]*/file outside of root /[a-z0-9\-\/]*`,
 }}
 
 func (s *S) TestExtract(c *C) {

internal/fsutil/create.go

@@ -42,7 +42,7 @@ type Entry struct {
 //
 // Create can return errors from the os package.
 func Create(options *CreateOptions) (*Entry, error) {
-	o, err := getValidOptions(options)
+	o, err := getValidCreateOptions(options)
 	if err != nil {
 		return nil, err
 	}
@@ -124,7 +124,7 @@ func Create(options *CreateOptions) (*Entry, error) {
 // information recorded in Entry. The Hash and Size attributes are set on
 // calling Close() on the Writer.
 func CreateWriter(options *CreateOptions) (io.WriteCloser, *Entry, error) {
-	o, err := getValidOptions(options)
+	o, err := getValidCreateOptions(options)
 	if err != nil {
 		return nil, nil, err
 	}
@@ -168,6 +168,10 @@ func createDir(o *CreateOptions) error {
 	}
 	err = os.Mkdir(path, o.Mode)
 	if os.IsExist(err) {
+		// TODO: Detect if existing content is a file. ErrExist is also returned
+		// if a file exists at this path, so returning nil here creates an
+		// inconsistency between our view of the content and the real content on
+		// disk.
 		return nil
 	}
 	return err
@@ -241,7 +245,7 @@ func createHardLink(o *CreateOptions) error {
 	return err
 }
 
-func getValidOptions(options *CreateOptions) (*CreateOptions, error) {
+func getValidCreateOptions(options *CreateOptions) (*CreateOptions, error) {
 	optsCopy := *options
 	o := &optsCopy
 	if o.Root == "" {
@@ -257,7 +261,7 @@ func getValidOptions(options *CreateOptions) (*CreateOptions, error) {
 func absPath(root, relPath string) (string, error) {
 	path := filepath.Clean(filepath.Join(root, relPath))
 	if !strings.HasPrefix(path, root) {
-		return "", fmt.Errorf("cannot create path %s outside of root %s", path, root)
+		return "", fmt.Errorf("cannot handle path %s outside of root %s", path, root)
 	}
 	return path, nil
 }

internal/fsutil/create_test.go

@@ -279,7 +279,7 @@ var createTests = []createTest{{
 		Mode: 0666,
 		Data: bytes.NewBufferString("hijacking system file"),
 	},
-	error: `cannot create path /file outside of root /root/`,
+	error: `cannot handle path /file outside of root /root/`,
 }, {
 	summary: "Hardlink cannot escape Root",
 	options: fsutil.CreateOptions{
@@ -410,7 +410,7 @@ var createWriterTests = []createWriterTest{{
 		Mode:        0644,
 		MakeParents: true,
 	},
-	error: `cannot create path /file outside of root /root/`,
+	error: `cannot handle path /file outside of root /root/`,
 }}
 
 func (s *S) TestCreateWriter(c *C) {

internal/fsutil/move.go

@@ -0,0 +1,81 @@
+package fsutil
+
+import (
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+)
+
+type MoveOptions struct {
+	SrcRoot string
+	DstRoot string
+	// Path is relative to SrcRoot.
+	Path string
+	Mode fs.FileMode
+	// If MakeParents is true, missing parent directories of Path are
+	// created with permissions 0755 in DstRoot.
+	MakeParents bool
+}
+
+// Move moves or creates a filesystem entry according to the provided options.
+//
+// Move can return errors from the os package.
+func Move(options *MoveOptions) error {
+	o, err := getValidMoveOptions(options)
+	if err != nil {
+		return err
+	}
+
+	srcPath, err := absPath(options.SrcRoot, o.Path)
+	if err != nil {
+		return err
+	}
+	dstPath, err := absPath(options.DstRoot, o.Path)
+	if err != nil {
+		return err
+	}
+
+	if o.MakeParents {
+		if err := os.MkdirAll(filepath.Dir(dstPath), 0o755); err != nil {
+			return err
+		}
+	}
+
+	switch o.Mode & fs.ModeType {
+	case 0, fs.ModeSymlink:
+		err = os.Rename(srcPath, dstPath)
+	case fs.ModeDir:
+		err = createDir(&CreateOptions{
+			Root:         o.DstRoot,
+			Path:         o.Path,
+			Mode:         o.Mode,
+			OverrideMode: true,
+		})
+	default:
+		err = fmt.Errorf("unsupported file type: %s", o.Path)
+	}
+	if err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func getValidMoveOptions(options *MoveOptions) (*MoveOptions, error) {
+	optsCopy := *options
+	o := &optsCopy
+	if o.SrcRoot == "" {
+		return nil, fmt.Errorf("internal error: MoveOptions.SrcRoot is unset")
+	}
+	if o.DstRoot == "" {
+		return nil, fmt.Errorf("internal error: MoveOptions.DstRoot is unset")
+	}
+	if o.SrcRoot != "/" {
+		o.SrcRoot = filepath.Clean(o.SrcRoot) + "/"
+	}
+	if o.DstRoot != "/" {
+		o.DstRoot = filepath.Clean(o.DstRoot) + "/"
+	}
+	return o, nil
+}