What

tsk undo-last — revert the most recent change to the task file. Single-step undo for the common "oops I just deleted/renamed the wrong thing" case.

Every Store.Save() now writes the previous on-disk contents to <path>.bak before atomically writing the new contents. tsk undo-last swaps the live file and the .bak.

Properties

• Single-step: only one snapshot ever exists. If you need durable history, that's git's job.
• Involutive: running undo-last twice returns to the state you had before the first undo, because the swap itself is a save.
• Best-effort: snapshot write failures (read-only FS, transient errors) never abort a save. The user's edit always lands; only the undo capability is at risk.
• Lazy snapshot: no .bak appears until at least one save modifies an existing file. A brand-new tsk add on an empty directory leaves no .bak behind. First-run users don't get a mysterious sidecar file.

Flags

Without --yes, the command prints what it's about to swap and waits for y/N.

Examples

$ tsk add "important thing"
added #1: important thing

$ tsk rm 1
removed 1 task(s)

$ tsk undo-last
About to swap /Users/sanjay/.tsk.md ↔ /Users/sanjay/.tsk.md.bak.
Continue? [y/N] y
restored /Users/sanjay/.tsk.md from /Users/sanjay/.tsk.md.bak

$ tsk ls
#1  important thing

Tests

5 new tests in internal/commands/undo_last_test.go:

• basic: add → rm → undo-last restores the task
• involutive: undo-last twice → back to post-rm state
• no snapshot → exits with friendly "no snapshot" error
• declining the prompt aborts and leaves the file untouched
• save creates .bak when the source file already exists; no .bak on first-ever save