Improve recover

- only save directories not referenced by any snapshot
- dont't write empty snapshot
- use progress bar

changelog/unreleased/pull-2880

@@ -0,0 +1,7 @@
+Enhancement: Improve recover command
+
+Restic recover used to generate a snapshot that contains all root trees
+even those which are already referenced by a snapshot.
+It now only processes trees not referenced at all.
+
+https://github.com/restic/restic/pull/2880

cmd/restic/cmd_recover.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"context"
 	"os"
 	"time"
 
@@ -11,11 +12,11 @@ import (
 
 var cmdRecover = &cobra.Command{
 	Use:   "recover [flags]",
-	Short: "Recover data from the repository",
+	Short: "Recover data from the repository not referenced by snapshots",
 	Long: `
 The "recover" command builds a new snapshot from all directories it can find in
-the raw data of the repository. It can be used if, for example, a snapshot has
-been removed by accident with "forget".
+the raw data of the repository which are not referenced in an existing snapshot.
+It can be used if, for example, a snapshot has been removed by accident with "forget".
 
 EXIT STATUS
 ===========
@@ -59,24 +60,14 @@ func runRecover(gopts GlobalOptions) error {
 	trees := make(map[restic.ID]bool)
 
 	for blob := range repo.Index().Each(gopts.ctx) {
-		if blob.Blob.Type != restic.TreeBlob {
-			continue
+		if blob.Type == restic.TreeBlob {
+			trees[blob.Blob.ID] = false
 		}
-		trees[blob.Blob.ID] = false
 	}
 
-	cur := 0
-	max := len(trees)
-	Verbosef("load %d trees\n\n", len(trees))
-
+	Verbosef("load %d trees\n", len(trees))
+	bar := newProgressMax(!gopts.Quiet, uint64(len(trees)), "trees loaded")
 	for id := range trees {
-		cur++
-		Verbosef("\rtree (%v/%v)", cur, max)
-
-		if !trees[id] {
-			trees[id] = false
-		}
-
 		tree, err := repo.LoadTree(gopts.ctx, id)
 		if err != nil {
 			Warnf("unable to load tree %v: %v\n", id.Str(), err)
@@ -84,26 +75,37 @@ func runRecover(gopts GlobalOptions) error {
 		}
 
 		for _, node := range tree.Nodes {
-			if node.Type != "dir" || node.Subtree == nil {
-				continue
+			if node.Type == "dir" && node.Subtree != nil {
+				trees[*node.Subtree] = true
 			}
-
-			subtree := *node.Subtree
-			trees[subtree] = true
 		}
+		bar.Add(1)
 	}
-	Verbosef("\ndone\n")
+	bar.Done()
+
+	Verbosef("load snapshots\n")
+	err = restic.ForAllSnapshots(gopts.ctx, repo, nil, func(id restic.ID, sn *restic.Snapshot, err error) error {
+		trees[*sn.Tree] = true
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+	Verbosef("done\n")
 
 	roots := restic.NewIDSet()
 	for id, seen := range trees {
-		if seen {
-			continue
+		if !seen {
+			Verboseff("found root tree %v\n", id.Str())
+			roots.Insert(id)
 		}
-
-		roots.Insert(id)
 	}
+	Printf("\nfound %d unreferenced roots\n", len(roots))
 
-	Verbosef("found %d roots\n", len(roots))
+	if len(roots) == 0 {
+		Verbosef("no snapshot to write.\n")
+		return nil
+	}
 
 	tree := restic.NewTree()
 	for id := range roots {
@@ -117,7 +119,7 @@ func runRecover(gopts GlobalOptions) error {
 			ModTime:    time.Now(),
 			ChangeTime: time.Now(),
 		}
-		err = tree.Insert(&node)
+		err := tree.Insert(&node)
 		if err != nil {
 			return err
 		}
@@ -133,19 +135,23 @@ func runRecover(gopts GlobalOptions) error {
 		return errors.Fatalf("unable to save blobs to the repo: %v", err)
 	}
 
-	sn, err := restic.NewSnapshot([]string{"/recover"}, []string{}, hostname, time.Now())
+	return createSnapshot(gopts.ctx, "/recover", hostname, []string{"recovered"}, repo, &treeID)
+
+}
+
+func createSnapshot(ctx context.Context, name, hostname string, tags []string, repo restic.Repository, tree *restic.ID) error {
+	sn, err := restic.NewSnapshot([]string{name}, tags, hostname, time.Now())
 	if err != nil {
 		return errors.Fatalf("unable to save snapshot: %v", err)
 	}
 
-	sn.Tree = &treeID
+	sn.Tree = tree
 
-	id, err := repo.SaveJSONUnpacked(gopts.ctx, restic.SnapshotFile, sn)
+	id, err := repo.SaveJSONUnpacked(ctx, restic.SnapshotFile, sn)
 	if err != nil {
 		return errors.Fatalf("unable to save snapshot: %v", err)
 	}
 
 	Printf("saved new snapshot %v\n", id.Str())
-
 	return nil
 }