backup: print full snapshot id in JSON summary

changelog/unreleased/issue-2724

@@ -0,0 +1,9 @@
+Change: Include full snapshot ID in JSON output of the bacukp command
+
+We have changed the JSON output of the backup command to include the full snapshot ID instead of just a shortened version.
+The latter can be ambiguous in rare cases.
+
+To derive the short ID, truncate the full ID down to 8 characters.
+
+https://github.com/restic/restic/issues/2724
+https://github.com/restic/restic/pull/3993

internal/ui/backup/json.go

@@ -191,7 +191,7 @@ func (b *JSONProgress) Finish(snapshotID restic.ID, start time.Time, summary *Su
 		TotalFilesProcessed: summary.Files.New + summary.Files.Changed + summary.Files.Unchanged,
 		TotalBytesProcessed: summary.ProcessedBytes,
 		TotalDuration:       time.Since(start).Seconds(),
-		SnapshotID:          snapshotID.Str(),
+		SnapshotID:          snapshotID.String(),
 		DryRun:              dryRun,
 	})
 }