Method canFastForwardToOrigin

src/node/worktree/WorktreeManager.ts:306–332

* Check if local trunk can fast-forward to origin/ . * Returns true if local is behind or equal to origin (safe to use origin). * Returns false if local is ahead or diverged (preserve local state).

(
    projectPath: string,
    trunkBranch: string,
    initLogger: InitLogger,
    abortSignal?: AbortSignal
  )

   * Returns false if local is ahead or diverged (preserve local state).
   */
  private async canFastForwardToOrigin(
    projectPath: string,
    trunkBranch: string,
    initLogger: InitLogger,
    abortSignal?: AbortSignal
  ): Promise<boolean> {
    try {
      // Check if local trunk is an ancestor of origin/trunk
      // Exit code 0 = local is ancestor (can fast-forward), non-zero = cannot
      using proc = execFileAsync(
        "git",
        ["-C", projectPath, "merge-base", "--is-ancestor", trunkBranch, `origin/${trunkBranch}`],
        abortSignal ? { signal: abortSignal } : undefined
      );
      await proc.result;
      return true; // Local is behind or equal to origin
    } catch (error) {
      if (isAbortError(error, abortSignal)) {
        throw error;
      }
      // Local is ahead or diverged - preserve local state
      initLogger.logStderr(
        `Note: Local ${trunkBranch} is ahead of or diverged from origin, using local state`
      );
      return false;
    }
  }

  /**
   * Fast-forward merge to latest origin/<trunkBranch> after checkout.