Obnam → blog → 2025 → Obnam 3: chunk repository, CLI convenience
  1. Goal
  2. Plan
  3. Notes
  4. Summary
  5. Comments?

Goal

I wasn't able to develop Obnam 3 last week, so this week I'm doing a session on Saturday.

Last time I implement subcommands for managing a chunk store. This time I'll integrate the chunk store to obnam chunk subcommands.

Plan

  • Add a global option obnam --chunks DIR that sets chunk store location.
  • Change obnam store commands to use the location set with the global option. Remove any location arguments from subcommands.
  • Change obnam chunk encode to use the global chunk store location, if an explicit filename isn't set.
  • Likewise obnam chunk decrypt.
  • Likewise obnam chunk inspect.

Notes

Prelude

  • Verify that tests still pass. They do.

Add global --repository option

  • On reflection, --chunks isn't a particularly clean option name, from a user point of view. It requires understanding that backups are stored as chunks. I'll use the option --repository instead. Since that is a long option name, I'll allow the alias -r as well.

  • Added the option.

  • Changed the obnam store subcommands to use the store location set with the option. Some day will want to add a configuration file that can set this, but one change at a time.

  • For the obnam chunk subcommands I'll want to continue to support using chunks without using the chunk store. However, I'll want to make using the store the default.

  • For obnam chunk encrypt there is already an --output option. If that's not used, fall back to using the chunk store. This means the command will lose the possibility of writing to the standard output. I can add that back later if there's a need.

  • For obnam chunk decrypt the chunk file is named on the command line. I'll change the subcommand to require either an option --id to specify the ID of a chunk in the chunk store, or --filename to specify a filename.

  • Likewise for obnam chunk inspect.

  • For testing this I will need to capture the chunk id in some way so that a later step can refer to it. Given how primitive the Subplot libraries for capturing output is, I'll want to avoid that. Instead, I'll add an option --id to obnam chunk encrypt that sets the ID. By default it picks a random one.

  • OK, after uninteresting side steps got this working.

  • Refactored code to reduce duplication by adding some helper functions the the Leaf trait to get or open the chunk repository.

Tidy up

  • Removed various eprintln calls for debugging and other cruft left in the coded base.
  • Verified that CI is happy.
  • Merged.

Summary

I reached my goal, and now obnam make use of the repository more convenient.

Comments?

If you have feedback on this development session, please use the following fediverse thread: https://toot.liw.fi/@liw/114641233721923242.