Port jj cheatsheets from ffi-playground into .cheat/jj

[alycda]

Ports the six jj cheatsheets from alycda/ffi-playground .devcontainer/jj/cheat/jj (at 081444c) into .cheat/jj/ here. Copied verbatim — no edits to content.

Why

They were stranded in a per-project devcontainer, but they answer the questions that come up mid-session in this repo, where jj is the daily driver: "I snapshotted a secret into @, now what?", "how do I fix a commit three deep without losing my place?"

Why .cheat/ and not tools/cheat/cheatsheets/community/jj/

cheat auto-detects a .cheat directory in the cwd and layers it onto the configured cheatpaths. So these are live the moment you're in the dotfiles checkout — no conf.nix change, no home-manager switch, nothing to wire up. It also keeps them honestly scoped: they encode this repo's jj-first workflow rather than claiming to be general community sheets. This is the pattern already documented in tools/cheat/README.md under "Local .cheat directories", and matches the existing top-level .cheat/ sheets (dev, devcontainer, docker/nix, nix/claude).

Contents

sheet	covers
branch	bookmarks vs branches, and that they don't auto-advance; v0.43's --named replacing --allow-new
edit-history	amending a mid-stack commit without moving @; v0.43's rebase -o replacing -d
ignore	the .gitignore-then-untrack ordering, and scrubbing a file already captured in earlier commits
log	revset recipes — local stack, by file, by date
squash	squash --from/--into, absorb, split
undo	undo, op log/op restore, evolog

Known overlap, deliberately not resolved here

tools/cheat/cheatsheets/community/jj/ holds five one-line stubs (branches, config, init, log, rebase). Only log collides by name, and the local .cheat copy wins while you're in the repo — so nothing breaks. Consolidating the two sets is left out so this stays a straight port; happy to follow up if you'd rather the community sheets absorb these instead.

Notes

• No Nix or module changes — .cheat/ needs no wiring, so statix/deadnix/nix flake check are unaffected.
• jj isn't installed in this sandbox, so this was committed with git per the fallback in CLAUDE.md.

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Generated by Claude Code

[github-actions]

⊕ Entity-level changes

.cheat/jj/branch

Status	Type	Name
+	chunk	lines 1-17

.cheat/jj/edit-history

Status	Type	Name
+	chunk	lines 1-12

.cheat/jj/ignore

Status	Type	Name
+	chunk	lines 1-15

.cheat/jj/log

Status	Type	Name
+	chunk	lines 1-17

.cheat/jj/squash

Status	Type	Name
+	chunk	lines 1-14

.cheat/jj/undo

Status	Type	Name
+	chunk	lines 1-17

Summary: 6 added across 6 files

_{functions and classes, not lines · sem}