Walk full DAG in entire checkpoint list and accept a git-style revrange

[Soph]

https://entire.io/gh/entireio/cli/trails/299

entire checkpoint list now mirrors git log semantics on every branch — checkpoints on merged feature branches are visible from main, and on a feature branch we no longer stop at commits reachable from main. To opt back into the old "feature-only" view (or scope to any other range), pass a positional revrange: A..B, A.. (= A..HEAD), ..B / B (full from B). Symmetric-difference (A...B) is rejected with a hint.

Same shift for entire checkpoint explain <id>'s associated-commits scan: default is now a full DAG walk capped at commitScanLimit. If the cap is hit with zero matches, it auto-falls back to an uncapped walk and prints a one-line Searching full history (no match in last N commits)… note. --search-all still skips straight to uncapped for callers who know the target is older than the cap.

Removes the now-unused computeReachableFromMain / walkFirstParentCommits helpers and their direct test.

Examples

# All checkpoints reachable from HEAD (default, includes merged branches)
entire checkpoint list

# Only checkpoints unique to this branch — the old feature-branch view
entire checkpoint list main..

# Checkpoints landed between two release tags
entire checkpoint list v0.5.0..v0.6.0

Test plan

• mise run check (fmt + lint + unit/integration/canary E2E) passes
• entire checkpoint list on a feature branch shows checkpoints reachable from HEAD, including those on merged branches
• entire checkpoint list main.. matches the prior feature-branch view
• entire checkpoint list main...HEAD errors with a hint
• entire checkpoint explain <id> for a checkpoint on a merged branch finds the associated commit without --search-all

---

Note

Medium Risk
Changes the default checkpoint/associated-commit discovery semantics to walk the full git DAG (including merged branches) and adds revision-range parsing, which could affect performance and the set/order of checkpoints shown. Risk is mitigated by scan caps with fallback behavior and expanded unit test coverage around merge scenarios and range parsing.

Overview
entire checkpoint list now accepts an optional positional git-style revision range (e.g. main.., A..B, <ref>) and defaults to git log-like reachability from HEAD, including checkpoints introduced via merged feature branches.

Checkpoint discovery for both the list view and entire explain <checkpoint> associated-commit lookup is refactored to walk the full DAG (instead of first-parent/default-branch filtering), with a bounded scan (commitScanLimit) and an automatic uncapped fallback that prints a one-line notice when needed. The PR removes the old first-parent/main-reachability helpers, updates CLI help/output labeling for scoped ranges, and adds/updates tests for merge-parent visibility, revision-range parsing, and the capped-scan fallback.

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[Copilot]

Pull request overview

This PR updates the checkpoint listing and checkpoint-to-commit association logic to match git log-style full-DAG reachability by default, and adds support for scoping entire checkpoint list to a git-style revision range (rejecting A...B with a hint). It also removes now-obsolete first-parent/default-branch filtering helpers.

Changes:

• entire checkpoint list now walks the full DAG from HEAD by default and accepts a positional revision range (A..B, A.., ..B, <ref>).
• entire checkpoint explain <id>’s associated-commit lookup now uses a bounded full-DAG scan with an automatic fallback to an unbounded scan when the cap is hit with zero matches.
• Tests updated for the new associated-commit behavior; parsing tests added for revision ranges.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
cmd/entire/cli/explain.go	Implements full-DAG walks for list/explain commit association, adds revision-range parsing + range-based checkpoint scanning.
cmd/entire/cli/explain_test.go	Updates associated-commit tests for new semantics; adds tests for fallback scan and revision-range parsing.
cmd/entire/cli/checkpoint_group.go	Extends checkpoint list command to accept an optional revision-range argument and updates help text.

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