# Extract checkpoint write helpers into treeWriter (no behavior change)

`9ae0014`→[main](/content/gh/entireio/cli/commits/main/index.html)·

Soph·2w ago·4 files·+356 added/-266 removed

Refactor toward the per-checkpoint git-ref store (#1471): isolate the repo-only
"build one checkpoint's subtree" machinery from the git-branch store so a second
backend can share it instead of duplicating it.

\- The repo-only entry/subtree builders (writeStandardCheckpointEntries,
writeTaskCheckpointEntries, writeSessionToSubdirectory, writeCheckpointSummary,
findSessionIndex, reaggregateFromEntries, replaceTranscript, replaceSkillEvents,
writeTranscript/writeCompactTranscript, copyMetadataDir, readSummaryFromBlob,
readMetadataFromBlob, buildCommitMessage) move from \*GitStore to a new
\*treeWriter; GitStore embeds \*treeWriter so call sites resolve via promotion.
\- GitStore's four write methods route through shared appliers anchored at the
checkpoint-dir root; the git-branch store keeps splicing the result under
<shard>/<id>/ into the v1 tree, so the committed v1 tree is byte-identical.
writeCheckpointSummary now takes the checkpoint-version to stamp.

Behavior-preserving: the git-branch checkpoint, strategy, and integration suites
are unchanged. Nothing constructs a second backend yet.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

## Sessions

99d650653e0cView transcript

## Changes

4

- cmd/entire/cli/checkpoint

- Mpersistent.go+327/-259

- Mpersistent_tripwire_test.go+1/-1

- Mpersistent_update_test.go+11/-3

- Mstore.go+17/-3

\n```
81 unmodified lines

// Use sharded path: <id[:2]>/<id[2:]>/
basePath := opts.CheckpointID.Path() + "/"
checkpointPath := opts.CheckpointID.Path()

// Flatten only the checkpoint subtree (O(files in checkpoint))
entries, err := s.flattenCheckpointEntries(rootTreeHash, checkpointPath)
// Build the new checkpoint subtree from its current state on the v1 branch,
// then splice it back at the shard path. basePath keeps the v1 sharded layout
// so stored session-file pointers stay /<shard>/<id>/<n>/... as before.
existing, err := s.subtreeObjAt(rootTreeHash, opts.CheckpointID.Path())
if err != nil {
return err
}

// Track task metadata path for commit trailer
var taskMetadataPath string

// Handle task checkpoints
if opts.IsTask && opts.ToolUseID != "" {
	taskMetadataPath, err = s.writeTaskCheckpointEntries(ctx, opts, basePath, entries)
	if err != nil {
		return err
	}
}

// Write standard checkpoint entries (transcript, prompts, context, metadata)
if err := s.writeStandardCheckpointEntries(ctx, opts, basePath, entries); err != nil {
	return plumbing.ZeroHash, ""
}

checkpointSubtree, taskMetadataPath, err := s.applySessionWrite(ctx, opts, existing, opts.CheckpointID.Path()+"/", CheckpointVersionBranchV1)
if err != nil {
	return err
}

// Build checkpoint subtree and splice into root (O(depth) tree surgery)
newTreeHash, err := s.spliceCheckpointSubtree(ctx, rootTreeHash, opts.CheckpointID, basePath, entries)
newTreeHash, err := s.spliceCheckpointSubtree(rootTreeHash, opts.CheckpointID, checkpointSubtree)
if err != nil {
	return err
}
}

return s.setPrimaryRef(newCommitHash)

// flattenCheckpointEntries reads only the entries under a specific checkpoint path
// from the sessions branch tree. This is O(files in checkpoint) instead of O(all checkpoints).
// Returns an empty map if the checkpoint doesn't exist yet.
func (s *GitStore) flattenCheckpointEntries(rootTreeHash plumbing.Hash, checkpointPath string) (map[string]object.TreeEntry, error) {
	entries := make(map[string]object.TreeEntry)
}

// subtreeObjAt returns the tree object for one checkpoint's subtree within a root
tree, or (nil, nil) when the root or the checkpoint path does not exist yet.
// path is the in-tree checkpoint path (e.g. "a3/b2c4d5e6f7"); pass "" to return
// the root tree itself (the per-checkpoint-ref layout, where the whole tree is
// the checkpoint subtree).
func (s *treeWriter) subtreeObjAt(rootTreeHash plumbing.Hash, path string) (*object.Tree, error) {
	if rootTreeHash == plumbing.ZeroHash {
		return entries, nil
	}
	return nil, nil //nolint:nilnil // absent checkpoint (no tree yet), not an error
}