# /simplify: tidy rewrite (resolveAuthor, thread refName, sparse tasks graft)

`b24e3ba`·

Soph·1w ago·2 files·+79 added/-46 removed

- Collapse the fallback name/email into a commitAuthor and extract resolveAuthor,
  shrinking rewriteCheckpoint's parameter list and de-duplicating the per-session
  and tasks-graft author fallback.
- Compute the ref name once in the walk and thread it through rewriteCheckpoint
  and graftTasksSubtree instead of recomputing RefName three times per checkpoint.
- Graft tasks with a single UpdateSubtree(MergeKeepExisting) call — splicing the
tasks/ entry into the root tree so sibling session subtrees keep their hashes —
instead of flattening and rebuilding the whole tree.
- Reset the ref only under --force (the non-force existing-ref case is already
  skipped by the caller), dropping a redundant check.
- Add a graft test covering the tasks splice (tasks/ added, existing entries
  preserved, checkpoint still reads back).

---

## Sessions

48ce721ba1a2View transcript

## Changes

2

- cmd/entire/cli/checkpoint

- Mrewrite.go+41/-46

- Mrewrite_test.go+38

```
54 unmodified lines
```

// tasksDirName is the checkpoint subtree that holds subagent task steps.
const tasksDirName = "tasks";

// commitAuthor is a git author identity.
type commitAuthor struct {
    Name  string
    Email string
}

// resolveAuthor returns the recorded author for a session, or the fallback when
// the session has no mapped commit author.
func resolveAuthor(sessionID string, authors map[string]commitAuthor, fallback commitAuthor) commitAuthor {
    if a, ok := authors[sessionID]; ok && a.Name != "" {
        return a
    }
    return fallback
}

// branchSessionAuthors maps each session id to the author of the earliest
// v1-branch commit that wrote it, so a rewrite can preserve the original author.
// The map is best-effort: a session with no resolvable commit falls back to the
// existing author.
refsStore *gitRefsStore,
repo *git.Repository,
cid id.CheckpointID,
refName plumbing.ReferenceName,
cpTreeHash plumbing.Hash,
authors map[string]commitAuthor,
fallbackName, fallbackEmail string,
fallback commitAuthor,
force bool,
) error {

// Start clean: drop any existing ref so the replay builds a fresh history
    // rooted at an orphan commit rather than parenting on stale content.
    refName, err := RefName(cid)
    if err != nil {
        return err
    }
    if _, err := repo.Reference(refName, true); err == nil {
        if err := repo.Storer.RemoveReference(refName); err != nil {
            return fmt.Errorf("reset existing ref: %w", err)
        }
    }

// Replay each session in order. Writing session N then its summary keeps
    // SessionSummary (which targets the latest session) pointed at the right one.
    for idx := range summary.Sessions {
        content, err := branch.ReadSessionContent(ctx, cid, idx)
        if err != nil {
            return fmt.Errorf("read session %d: %w", idx, err)
        }
        m := content.Metadata
        name, email := fallbackName, fallbackEmail
        author := resolveAuthor(m.SessionID, authors, fallback)

if err := refsStore.Write(ctx, Session(WriteOptions{
            AuthorName:                  name,
            AuthorEmail:                 email,
            AuthorName:                  author.Name,
            AuthorEmail:                 author.Email,
            Agent:                       m.Agent,
            Model:                       m.Model,
            TurnID:                      m.TurnID,
        })); err != nil {
            return fmt.Errorf("write session: %w", err)
        }
    }

return nil
}

// graftTasksSubtree adds the tasks/ subtree to the checkpoint's current ref tree
// via one commit on top, reusing the existing task objects unchanged.
func graftTasksSubtree(ctx context.Context, repo *git.Repository, refsStore *gitRefsStore, cid id.CheckpointID, tasksHash plumbing.Hash, author commitAuthor) error {
    refName, err := RefName(cid)
    if err != nil {
        return err
    }
    // additional implementation details...
}

```