Draw squash-merged branches as merged in the Graph

[danipen]

Problem

Repos that land pull requests with squash (or rebase) merges — e.g. a merge queue configured to squash — leave no merge commit behind. The branch tip never becomes an ancestor of the default branch, so the Graph drew finished PRs as live, unmerged branches, next to real-merge PRs that did read as merged. Confusing.

Fix

Recover the landing by content instead of ancestry:

• Renderer (pure, graph/squash.ts) — from the loaded window, find branch tips not reachable from the default branch (local or remote, whichever is newer) and each tip's merge base with it.
• Main (git/read/squash-landings.ts) — a branch landed when a mainline commit newer than its merge base has the same patch-id --stable as the branch's whole base..tip diff (squash) or its tip commit (rebase merge). Three streamed patch-id passes (the diff-tree --stdin pipeline, generalised to also diff ranges via <tip> <base> lines) — never a spawn per branch.
• Layout — a squash-landed tip counts as merged everywhere a merge source does (Hide merged, claim priority, structure-only, upstream comparison, packing lead-out) and gets a new squash edge into its landing commit.
• Render — the squash edge is drawn exactly like a merge (solid connector, the landing wears the branch's merge ring): the branch IS merged. A dash was tried and rejected — dashes already mean WIP / guessed names / backport twins here, so it read as "pending".
• Detail pane — the one place the missing ancestry is named: selecting a landing commit shows "Squash of <branch>", linking to that branch's changes view.

The hook only re-asks when the mainline tip or candidate set changes, and keeps the last answer while loading, so watcher refreshes don't re-run git or flicker.

Tests

• Integration (squash-landings.test.ts, real git): multi-commit squash merge, rebase merge, never-landed branch, base cutoff.
• Unit (squash.test.ts): candidate/merge-base derivation, remote-ahead default branch, synced branches, tags/HEAD/out-of-window skips.
• Unit: squashedBranchesByLanding (landing → squashed branches).
• Layout: squash edge + ring, Hide merged, upstream, structure-only, out-of-window landings.

Verified visually on a squash-merge-queue repo: all four squash-landed branches connect into their (#N) commit like merges; the landing's detail pane names the squashed branch and opens it (same files/stat as the squash commit).

🤖 Generated with Claude Code