Add store prune --dry-run

[TyceHerrman]

could store prune get a --dry-run flag added to it?

[jdx]

Sure — #1228 adds it.

It runs the identical walk and every skip decision a real prune makes (index-referenced, nlink > 1, exec-marker companion check) and just never unlinks:

$ aube store prune --dry-run
Would prune 412 files (up to 18.7 MB) from the store

The size is an upper bound, hence "up to" — a real prune credits bytes only after the unlink succeeds so a permission-denied file can't inflate the "freed" total, and a dry run has no unlink to check.

Output is a count plus a size rather than a file listing, deliberately: a prunable file is by definition referenced by no cached index, so there's no package name to attribute it to and aube find-hash returns nothing for it. A list of bare hashes wouldn't tell you anything you could act on. If you were hoping for per-package output, say so and I'll take another look — it would need the prune walk to grow a different notion of ownership than it has today.

AI-assisted — Tool: Claude Code; model: anthropic/claude-opus-5; version: 2.1.220.