Reduce startup git work for workspace snapshots

2026-07-29 12:01:31 +00:00 · 2026-05-27 20:18:49 +07:00
parent dbfd42da46
commit 5d8dc800fc
13 changed files with 862 additions and 57 deletions
--- a/docs/diagnostics/git-snapshot-startup-reshaping-2026-05-27.md
+++ b/docs/diagnostics/git-snapshot-startup-reshaping-2026-05-27.md
@@ -0,0 +1,173 @@
+# Git Snapshot Startup Reshaping - 2026-05-27
+
+## What changed
+
+The sidebar PR badge no longer has a special per-row fetch path. It is derived from the workspace snapshot, the same way the sidebar already gets branch/diff metadata.
+
+```text
+daemon startup / workspace subscription
+  -> WorkspaceGitService.refreshSnapshot(cwd)
+    -> getCheckoutSnapshotFacts(cwd)
+    -> getCheckoutStatus(cwd, { facts })
+    -> getCheckoutShortstat(cwd, { facts })
+    -> getPullRequestStatus(cwd, github, ..., { facts })
+    -> WorkspaceGitRuntimeSnapshot
+  -> session workspace descriptor githubRuntime.pullRequest
+  -> app useSidebarWorkspacesList()
+  -> SidebarWorkspaceEntry.prHint
+  -> Sidebar row badge + hover card checks
+```
+
+The remaining `checkout_pr_status_request` path is still present for explicit PR surfaces and compatibility, but the sidebar row badge no longer calls `useWorkspacePrHint()` and therefore no longer generates ad hoc checkout PR status requests per visible row.
+
+## Shared Git Facts
+
+`getCheckoutSnapshotFacts()` is now the first git read in the workspace snapshot builder. It gathers facts that were previously rediscovered by separate functions:
+
+- worktree root: `rev-parse --show-toplevel`
+- current branch: `rev-parse --abbrev-ref HEAD`
+- origin remote URL
+- Paseo worktree ownership and stored base ref
+- resolved base ref and best comparison base
+- main repo root
+- branch remote/merge config
+- tracked origin branch
+- pull request lookup target for fork/PR worktrees
+
+Those facts are then passed through `CheckoutContext` so status, shortstat, and PR status reuse the same answers instead of independently re-reading them.
+
+## Current Data Flow
+
+```text
+Workspace subscription / fetch_workspaces
+  -> session workspace registry
+  -> workspaceGitService.getSnapshot(cwd, includeGitHub)
+     -> refresh queue/throttle/dedupe per normalized cwd
+     -> refreshGitSnapshot()
+        -> getCheckoutSnapshotFacts()
+        -> getCheckoutStatus({ facts })
+        -> getCheckoutShortstat({ facts })
+     -> refreshGitHubSnapshot()
+        -> getPullRequestStatus({ facts })
+     -> cached WorkspaceGitRuntimeSnapshot
+  -> WorkspaceDescriptorPayload.gitRuntime
+  -> WorkspaceDescriptorPayload.githubRuntime
+  -> app session store
+  -> useSidebarWorkspacesList()
+     -> diffStat from descriptor
+     -> prHint from descriptor.githubRuntime.pullRequest
+```
+
+## Startup Benchmark
+
+Added deterministic real-home benchmark:
+
+`packages/server/scripts/benchmark-startup-git-real-home.ts`
+
+The script freezes the current Paseo home using the same metadata-copy shape as `scripts/dev-home.sh`: JSON under `agents`, JSON under `projects`, and `config.json`. It then starts an isolated in-process daemon against that frozen home, subscribes to workspaces/agents, records git invocations through `runGitCommand`, and reports elapsed time, git count, max concurrency, CPU, and memory deltas.
+
+The frozen home used for the comparison contained 22 workspaces.
+
+### Before/After
+
+| run         | code shape    | client shape                              | git commands | failures | elapsed |
+| ----------- | ------------- | ----------------------------------------- | -----------: | -------: | ------: |
+| baseline    | before change | legacy sidebar PR fanout                  |          529 |       20 | 39039ms |
+| split check | after change  | legacy sidebar PR fanout                  |          375 |       15 | 39039ms |
+| after       | after change  | snapshot-only sidebar, no PR badge fanout |          372 |       15 | 31273ms |
+
+The server-side fact reuse accounts for nearly all measured git command reduction: `529 -> 375` (`-154`, `-29.1%`) even when the old PR fanout is still forced. Removing the sidebar fanout removes the ad hoc request path, but in this run it only changed command count by `3` because the refreshed workspace snapshots already carried the PR data by the time the fanout ran.
+
+### Baseline: before change + legacy PR fanout
+
+```json
+{
+  "scenario": "legacyPrFanout",
+  "workspaceCount": 22,
+  "elapsedMs": 39039,
+  "git": {
+    "total": 529,
+    "failed": 20,
+    "maxConcurrent": 8,
+    "byCommand": [
+      { "key": "show-ref --verify --quiet refs/heads/main", "count": 66 },
+      { "key": "rev-parse --git-common-dir", "count": 58 },
+      { "key": "rev-parse --abbrev-ref HEAD", "count": 50 },
+      { "key": "rev-parse --git-dir", "count": 36 },
+      { "key": "show-ref --verify --quiet refs/remotes/origin/main", "count": 35 },
+      { "key": "symbolic-ref --quiet refs/remotes/origin/HEAD", "count": 35 },
+      { "key": "config --get remote.origin.url", "count": 32 },
+      { "key": "ls-files --others --exclude-standard", "count": 18 },
+      { "key": "rev-parse --absolute-git-dir", "count": 18 },
+      { "key": "merge-base HEAD origin/main", "count": 17 },
+      { "key": "rev-parse --show-toplevel", "count": 14 },
+      { "key": "status --porcelain", "count": 14 }
+    ]
+  },
+  "process": {
+    "cpuUserMs": 2009,
+    "cpuSystemMs": 2428,
+    "rssDeltaMb": -1.5,
+    "heapUsedDeltaMb": 16.9
+  }
+}
+```
+
+### After: after change + snapshot-only sidebar
+
+```json
+{
+  "scenario": "snapshotOnly",
+  "workspaceCount": 22,
+  "elapsedMs": 31273,
+  "git": {
+    "total": 372,
+    "failed": 15,
+    "maxConcurrent": 8,
+    "byCommand": [
+      { "key": "config --get remote.origin.url", "count": 35 },
+      { "key": "show-ref --verify --quiet refs/heads/main", "count": 34 },
+      { "key": "rev-parse --git-common-dir", "count": 31 },
+      { "key": "show-ref --verify --quiet refs/remotes/origin/main", "count": 22 },
+      { "key": "status --porcelain", "count": 22 },
+      { "key": "ls-files --others --exclude-standard", "count": 18 },
+      { "key": "rev-parse --absolute-git-dir", "count": 18 },
+      { "key": "merge-base HEAD origin/main", "count": 17 },
+      { "key": "rev-parse --abbrev-ref HEAD", "count": 17 },
+      { "key": "rev-parse --show-toplevel", "count": 17 },
+      { "key": "symbolic-ref --quiet refs/remotes/origin/HEAD", "count": 17 },
+      { "key": "rev-list --count main..origin/main", "count": 7 }
+    ]
+  },
+  "process": {
+    "cpuUserMs": 1871,
+    "cpuSystemMs": 2152,
+    "rssDeltaMb": 4.4,
+    "heapUsedDeltaMb": 8.8
+  }
+}
+```
+
+## Snapshot Equivalence Guard
+
+Added a focused utility test proving that status, shortstat, and PR status return the same data when run from shared snapshot facts. The same test records git calls and asserts the facts-backed path does not re-run:
+
+- `rev-parse --show-toplevel`
+- `rev-parse --abbrev-ref HEAD`
+
+Test:
+
+`packages/server/src/utils/checkout-git.test.ts` -> `reuses checkout snapshot facts across status, shortstat, and PR status reads`
+
+## Remaining Waste Visible In Baseline
+
+This pass reshaped the data flow and removed the sidebar PR badge special path. It did not try to optimize every command.
+
+The benchmark still shows repeated per-workspace reads that are candidates for the next pass:
+
+- origin URL lookup repeats across snapshot facts and GitHub remote resolution paths.
+- base ref existence checks still repeat as `show-ref` probes.
+- repo/worktree identity still requires one root/current-branch rev-parse per workspace.
+- shortstat still runs its own merge-base/diff/untracked scan per workspace.
+
+The important invariant now is clearer: sidebar-visible git data should flow from `WorkspaceGitService` snapshots, and snapshot builders should receive reusable git facts through `CheckoutContext`.