tag: output the original ID and new snapshotID (#5144)

* tag: output the original ID and new snapshotID

tag: print changed snapshot information immediately

* print changed snapshot immediately after it has been saved
* add message type to the changedSnapshot
* add a summary type which will share the JSON output of the numer of changed snapshots
* updated verbosity of the changed snapshot in text mode to only work when verbosity > 2
* also use the terminal status printer for a standard handling for stdout messages

changelog/unreleased/issue-5137

@@ -0,0 +1,8 @@
+Enhancement: Restic tag command returns the modified snapshot information
+
+Restic `tag` command now returns the modified snapshot information in the
+output. Added `--json` option to the command to get the output in JSON format
+for scripting access.
+
+https://github.com/restic/restic/issues/5137
+https://github.com/restic/restic/pull/5144

cmd/restic/cmd_tag.go

@@ -9,6 +9,8 @@ import (
 	"github.com/restic/restic/internal/errors"
 	"github.com/restic/restic/internal/repository"
 	"github.com/restic/restic/internal/restic"
+	"github.com/restic/restic/internal/ui"
+	"github.com/restic/restic/internal/ui/termstatus"
 )
 
 var cmdTag = &cobra.Command{
@@ -34,7 +36,9 @@ Exit status is 12 if the password is incorrect.
 	GroupID:           cmdGroupDefault,
 	DisableAutoGenTag: true,
 	RunE: func(cmd *cobra.Command, args []string) error {
-		return runTag(cmd.Context(), tagOptions, globalOptions, args)
+		term, cancel := setupTermstatus()
+		defer cancel()
+		return runTag(cmd.Context(), tagOptions, globalOptions, term, args)
 	},
 }
 
@@ -58,7 +62,18 @@ func init() {
 	initMultiSnapshotFilter(tagFlags, &tagOptions.SnapshotFilter, true)
 }
 
-func changeTags(ctx context.Context, repo *repository.Repository, sn *restic.Snapshot, setTags, addTags, removeTags []string) (bool, error) {
+type changedSnapshot struct {
+	MessageType   string    `json:"message_type"` // changed
+	OldSnapshotID restic.ID `json:"old_snapshot_id"`
+	NewSnapshotID restic.ID `json:"new_snapshot_id"`
+}
+
+type changedSnapshotsSummary struct {
+	MessageType      string `json:"message_type"` // summary
+	ChangedSnapshots int    `json:"changed_snapshots"`
+}
+
+func changeTags(ctx context.Context, repo *repository.Repository, sn *restic.Snapshot, setTags, addTags, removeTags []string, printFunc func(changedSnapshot)) (bool, error) {
 	var changed bool
 
 	if len(setTags) != 0 {
@@ -87,7 +102,7 @@ func changeTags(ctx context.Context, repo *repository.Repository, sn *restic.Sna
 			return false, err
 		}
 
-		debug.Log("new snapshot saved as %v", id)
+		debug.Log("old snapshot %v saved as a new snapshot %v", sn.ID(), id)
 
 		// Remove the old snapshot.
 		if err = repo.RemoveUnpacked(ctx, restic.WriteableSnapshotFile, *sn.ID()); err != nil {
@@ -95,11 +110,13 @@ func changeTags(ctx context.Context, repo *repository.Repository, sn *restic.Sna
 		}
 
 		debug.Log("old snapshot %v removed", sn.ID())
+
+		printFunc(changedSnapshot{MessageType: "changed", OldSnapshotID: *sn.ID(), NewSnapshotID: id})
 	}
 	return changed, nil
 }
 
-func runTag(ctx context.Context, opts TagOptions, gopts GlobalOptions, args []string) error {
+func runTag(ctx context.Context, opts TagOptions, gopts GlobalOptions, term *termstatus.Terminal, args []string) error {
 	if len(opts.SetTags) == 0 && len(opts.AddTags) == 0 && len(opts.RemoveTags) == 0 {
 		return errors.Fatal("nothing to do!")
 	}
@@ -114,24 +131,44 @@ func runTag(ctx context.Context, opts TagOptions, gopts GlobalOptions, args []st
 	}
 	defer unlock()
 
-	changeCnt := 0
+	printFunc := func(c changedSnapshot) {
+		Verboseff("old snapshot ID: %v -> new snapshot ID: %v\n", c.OldSnapshotID, c.NewSnapshotID)
+	}
+
+	summary := changedSnapshotsSummary{MessageType: "summary", ChangedSnapshots: 0}
+	printSummary := func(c changedSnapshotsSummary) {
+		if c.ChangedSnapshots == 0 {
+			Verbosef("no snapshots were modified\n")
+		} else {
+			Verbosef("modified %v snapshots\n", c.ChangedSnapshots)
+		}
+	}
+
+	if gopts.JSON {
+		printFunc = func(c changedSnapshot) {
+			term.Print(ui.ToJSONString(c))
+		}
+		printSummary = func(c changedSnapshotsSummary) {
+			term.Print(ui.ToJSONString(c))
+		}
+	}
+
 	for sn := range FindFilteredSnapshots(ctx, repo, repo, &opts.SnapshotFilter, args) {
-		changed, err := changeTags(ctx, repo, sn, opts.SetTags.Flatten(), opts.AddTags.Flatten(), opts.RemoveTags.Flatten())
+		changed, err := changeTags(ctx, repo, sn, opts.SetTags.Flatten(), opts.AddTags.Flatten(), opts.RemoveTags.Flatten(), printFunc)
 		if err != nil {
 			Warnf("unable to modify the tags for snapshot ID %q, ignoring: %v\n", sn.ID(), err)
 			continue
 		}
 		if changed {
-			changeCnt++
+			summary.ChangedSnapshots++
 		}
 	}
+
 	if ctx.Err() != nil {
 		return ctx.Err()
 	}
-	if changeCnt == 0 {
-		Verbosef("no snapshots were modified\n")
-	} else {
-		Verbosef("modified tags on %v snapshots\n", changeCnt)
-	}
+
+	printSummary(summary)
+
 	return nil
 }

cmd/restic/cmd_tag_integration_test.go

@@ -9,7 +9,7 @@ import (
 )
 
 func testRunTag(t testing.TB, opts TagOptions, gopts GlobalOptions) {
-	rtest.OK(t, runTag(context.TODO(), opts, gopts, []string{}))
+	rtest.OK(t, runTag(context.TODO(), opts, gopts, nil, []string{}))
 }
 
 // nolint: staticcheck // false positive nil pointer dereference check

doc/075_scripting.rst

@@ -722,6 +722,30 @@ The stats command returns a single JSON object.
 | ``compression_space_saving`` | Overall space saving due to compression             |
 +------------------------------+-----------------------------------------------------+
 
+tag
+---
+
+The ``tag`` command uses the JSON lines format with the following message types.
+
+Changed
+^^^^^^^
+
++--------------------------+-------------------------------------------+
+| ``message_type``         | Always "changed"                          |
++--------------------------+-------------------------------------------+
+| ``old_snapshot_id``      | ID of the snapshot before the change      |
++--------------------------+-------------------------------------------+
+| ``new_snapshot_id``      | ID of the snapshot after the change       |
++--------------------------+-------------------------------------------+
+
+Summary
+^^^^^^^
+
++-----------------------------+-------------------------------------------+
+| ``message_type``            | Always "summary"                          |
++-----------------------------+-------------------------------------------+
+| ``changed_snapshot_count``  | Total number of changed snapshots         |
++-----------------------------+-------------------------------------------+
 
 version
 -------