Add pks rm and bump the version to 0.6.0

[dduugg]

Summary

pks rm packs/foo deletes a pack along with what other packs say about it. It removes the pack from their dependencies, ignored_dependencies and visible_to lists, drops the violations their package_todo.yml files record on it (deleting a todo file that ends up empty), and then deletes the pack's directory. Deleting the directory by hand leaves pks validate failing on dependencies that name a missing pack (packwerk-extensions rejects such visible_to entries too) and pks check failing on stale todo entries.

Unless given --force, it refuses to remove a pack that other packs may still use, because once the pack is gone check can't see their references to it:

• If other packs reference its constants, it lists each one as file:line:column and the constant.
• If it has Ruby files under lib/ (other than lib/tasks/) that are outside the autoload roots, the Zeitwerk resolver never learns their constants, so references to them can't be checked. Gem-style packs keep their code there, and without this check a gem pack used across a large app was deleted without objection. The experimental parser reads definitions from every file, so the check is skipped with it.

The root pack can't be removed, and neither can a pack with other packs nested inside it, even with --force.

This PR also bumps the version to 0.6.0, so merging it releases v0.6.0.

Fixes #16.

Release

• auto-release.yml dispatches the v0.6.0 release once this lands on main, since Cargo.toml's version has no tag yet. 0.6.0 is a minor bump because pks rm is a new feature.
• ## Unreleased in the CHANGELOG is now ## 0.6.0, the heading dist takes the release notes from.
• e09f637 adds an entry for the warm-cache speedup from Skip reading source files on a warm cache hit via mtime + length #59, the one user-visible change since 0.5.0 that didn't have one.

How this relates to #60

• This PR doesn't depend on Preserve comments when auto-correcting unused dependencies #60 and can merge first.
• Each package.yml that rm changes is rewritten through write_pack_to_disk, as add-dependency and check-unused-dependencies --auto-correct do on main, so the file loses its comments and takes pks's key order. Preserve comments when auto-correcting unused dependencies #60 edits these lists as text instead, and once it lands rm can do the same.
• tests/rm_test.rs has two ignored tests for that: a removal that keeps comments and key order, and the warning when a flow-style list has to be rewritten. Both fail today and pass against a build of rm that uses Preserve comments when auto-correcting unused dependencies #60's edit. Preserve comments when auto-correcting unused dependencies #60 should switch rm over and enable them before it merges.

Commits

• 0841234 makes package_todo.yml writes return errors instead of panicking, so rm can report them.
• 15a463e adds rm.
• e09f637 bumps the version and prepares the CHANGELOG.

Design notes

• Todo files lose only the removed pack's entries. Regenerating them with pks update would also pick up any unrelated drift.
• The directory is deleted last. A partial delete can take package.yml with it, and then rm could no longer find the pack to clean up the references to it.

Who this affects

• pks rm is new.
• pks update reports a failure to write a todo file as an error and exits 2, where it used to panic.

Test plan

• tests/rm_test.rs: a removal that touches every kind of reference, checked byte for byte and followed by passing validate and check; refusals for references, for unresolvable lib/ code, and for both at once, each leaving the fixture unchanged; --force; the root pack; nested packs; an unknown pack; and a trailing slash.
• Breaking the lib/tasks/ exclusion fails a test.
• On copies of two large apps, refusals listed 2,461 and 248 references and changed nothing. After forced removals, the todo files had lost only the removed pack's blocks and validate passed in both. check matched its baseline in one, and in the other reported the leftover references against the pack that defines an enclosing namespace, which is how the resolver already treats a missing constant.
• pks --version prints pks 0.6.0, and CHANGELOG.md has the exact ## 0.6.0 heading that auto-release.yml checks for.
• cargo test (333 passed, 2 ignored), fmt, and clippy with -Dwarnings.
• CI passes.

[iMacTia]

Heya, really keen on getting v0.6.0 released with the ERB fix.
I understand this is currently blocked by #60, is there anything I could do to help move this forward?
If #60 won't budge anytime soon, could we rebase this on top of main and postpone that fix to 0.7.0?

[dduugg]

Thanks for the nudge. I've rebuilt this on main without #60, so it can merge on its own and release 0.6.0 with the ERB fixes.

The cost is that pks rm now rewrites each package.yml it changes, the way add-dependency does, so those files lose their comments and key order until #60 lands. The tests for #60's behavior are still in tests/rm_test.rs, ignored, for #60 to enable once it switches rm over.