Snapshot: Add Original ID

The Original ID is used when the snapshot is modified (e.g. by `tag`
command). Adjust integration testing to assert correctness.

src/cmds/restic/cmd_tag.go

@@ -76,6 +76,11 @@ func changeTags(repo *repository.Repository, snapshotID restic.ID, setTags, addT
 	}
 
 	if changed {
+		// Retain the original snapshot id over all tag changes.
+		if sn.Original == nil {
+			sn.Original = sn.ID()
+		}
+
 		// Save the new snapshot.
 		id, err := repo.SaveJSONUnpacked(restic.SnapshotFile, sn)
 		if err != nil {

src/cmds/restic/integration_test.go

@@ -670,6 +670,9 @@ func TestTag(t *testing.T) {
 		Assert(t, newest != nil, "expected a new backup, got nil")
 		Assert(t, len(newest.Tags) == 0,
 			"expected no tags, got %v", newest.Tags)
+		Assert(t, newest.Original == nil,
+			"expected original ID to be nil, got %v", newest.Original)
+		originalID := *newest.ID
 
 		testRunTag(t, TagOptions{SetTags: []string{"NL"}}, gopts)
 		testRunCheck(t, gopts)
@@ -677,6 +680,9 @@ func TestTag(t *testing.T) {
 		Assert(t, newest != nil, "expected a new backup, got nil")
 		Assert(t, len(newest.Tags) == 1 && newest.Tags[0] == "NL",
 			"set failed, expected one NL tag, got %v", newest.Tags)
+		Assert(t, newest.Original != nil, "expected original snapshot id, got nil")
+		Assert(t, *newest.Original == originalID,
+			"expected original ID to be set to the first snapshot id")
 
 		testRunTag(t, TagOptions{AddTags: []string{"CH"}}, gopts)
 		testRunCheck(t, gopts)
@@ -684,6 +690,9 @@ func TestTag(t *testing.T) {
 		Assert(t, newest != nil, "expected a new backup, got nil")
 		Assert(t, len(newest.Tags) == 2 && newest.Tags[0] == "NL" && newest.Tags[1] == "CH",
 			"add failed, expected CH,NL tags, got %v", newest.Tags)
+		Assert(t, newest.Original != nil, "expected original snapshot id, got nil")
+		Assert(t, *newest.Original == originalID,
+			"expected original ID to be set to the first snapshot id")
 
 		testRunTag(t, TagOptions{RemoveTags: []string{"NL"}}, gopts)
 		testRunCheck(t, gopts)
@@ -691,6 +700,9 @@ func TestTag(t *testing.T) {
 		Assert(t, newest != nil, "expected a new backup, got nil")
 		Assert(t, len(newest.Tags) == 1 && newest.Tags[0] == "CH",
 			"remove failed, expected one CH tag, got %v", newest.Tags)
+		Assert(t, newest.Original != nil, "expected original snapshot id, got nil")
+		Assert(t, *newest.Original == originalID,
+			"expected original ID to be set to the first snapshot id")
 
 		testRunTag(t, TagOptions{AddTags: []string{"US", "RU"}}, gopts)
 		testRunTag(t, TagOptions{RemoveTags: []string{"CH", "US", "RU"}}, gopts)
@@ -699,6 +711,9 @@ func TestTag(t *testing.T) {
 		Assert(t, newest != nil, "expected a new backup, got nil")
 		Assert(t, len(newest.Tags) == 0,
 			"expected no tags, got %v", newest.Tags)
+		Assert(t, newest.Original != nil, "expected original snapshot id, got nil")
+		Assert(t, *newest.Original == originalID,
+			"expected original ID to be set to the first snapshot id")
 
 		// Check special case of removing all tags.
 		testRunTag(t, TagOptions{SetTags: []string{""}}, gopts)
@@ -707,6 +722,9 @@ func TestTag(t *testing.T) {
 		Assert(t, newest != nil, "expected a new backup, got nil")
 		Assert(t, len(newest.Tags) == 0,
 			"expected no tags, got %v", newest.Tags)
+		Assert(t, newest.Original != nil, "expected original snapshot id, got nil")
+		Assert(t, *newest.Original == originalID,
+			"expected original ID to be set to the first snapshot id")
 	})
 }
 

src/restic/snapshot.go

@@ -21,6 +21,7 @@ type Snapshot struct {
 	GID      uint32    `json:"gid,omitempty"`
 	Excludes []string  `json:"excludes,omitempty"`
 	Tags     []string  `json:"tags,omitempty"`
+	Original *ID       `json:"original,omitempty"`
 
 	id *ID // plaintext ID, used during restore
 }