Ask foranything.

  private async take(
    cwd: string,
    source: TakeSource,
  ): Promise<void | { background: true }> {
    const head = await git(cwd, ["rev-parse", "HEAD"]);
    const plan = await classifyUpdate(cwd, head, source.ref);
    this.options.log("app-source.take-planned", {
      from: source.kind,
      kind: plan.kind,
    });
    if (plan.kind === "none") throw new Error(source.emptyMessage);
    let to = plan.kind === "fast-forward" ? plan.tip : "";
    if (plan.kind === "conflict") {
      return await this.dispatchMerge(cwd, source, source.brief(plan, head));
    }
    if (plan.kind === "clean") {
      // The merge exists as objects only: nothing is checked out and the
      // checkout's branch has not moved, so giving up here leaves no state.
      to = await git(
        cwd,
        ["commit-tree", plan.tree, "-p", head, "-p", plan.tip, "-m", source.subject],
        { env: await this.identityEnv(cwd) },
      );
      if (!(source.trustIdenticalTree && plan.identical)) {
        const gate = await checkMergedUpdate(cwd, to, this.options.updateScratchDir);
        if (!gate.ok) {
          return await this.dispatchMerge(cwd, source, source.brief(plan, head, gate.output));
        }
      }
    }
    // No line in the chat for this: it applied while the user watched the
    // button, exactly like a fast-forward.
    await git(cwd, ["merge", "--ff-only", to]);
    await source.settle?.(to);
    await this.swapIn(cwd, head, to);
  }

  private async take(
    cwd: string,
    source: TakeSource,
  ): Promise<void | { background: true }> {
    const head = await git(cwd, ["rev-parse", "HEAD"]);
    const plan = await classifyUpdate(cwd, head, source.ref);
    this.options.log("app-source.take-planned", {
      from: source.kind,
      kind: plan.kind,
    });
    if (plan.kind === "none") throw new Error(source.emptyMessage);
    let to = plan.kind === "fast-forward" ? plan.tip : "";
    if (plan.kind === "conflict") {
      return await this.dispatchMerge(cwd, source, source.brief(plan, head));
    }
    if (plan.kind === "clean") {
      // The merge exists as objects only: nothing is checked out and the
      // checkout's branch has not moved, so giving up here leaves no state.
      to = await git(
        cwd,
        ["commit-tree", plan.tree, "-p", head, "-p", plan.tip, "-m", source.subject],
        { env: await this.identityEnv(cwd) },
      );
      if (!(source.trustIdenticalTree && plan.identical)) {
        const gate = await checkMergedUpdate(cwd, to, this.options.updateScratchDir);
        if (!gate.ok) {
          return await this.dispatchMerge(cwd, source, source.brief(plan, head, gate.output));
        }
      }
    }
    // No line in the chat for this: it applied while the user watched the
    // button, exactly like a fast-forward.
    await git(cwd, ["merge", "--ff-only", to]);
    await source.settle?.(to);
    await this.swapIn(cwd, head, to);
  }

  private async take(
    cwd: string,
    source: TakeSource,
  ): Promise<void | { background: true }> {
    const head = await git(cwd, ["rev-parse", "HEAD"]);
    const plan = await classifyUpdate(cwd, head, source.ref);
    this.options.log("app-source.take-planned", {
      from: source.kind,
      kind: plan.kind,
    });
    if (plan.kind === "none") throw new Error(source.emptyMessage);
    let to = plan.kind === "fast-forward" ? plan.tip : "";
    if (plan.kind === "conflict") {
      return await this.dispatchMerge(cwd, source, source.brief(plan, head));
    }
    if (plan.kind === "clean") {
      // The merge exists as objects only: nothing is checked out and the
      // checkout's branch has not moved, so giving up here leaves no state.
      to = await git(
        cwd,
        ["commit-tree", plan.tree, "-p", head, "-p", plan.tip, "-m", source.subject],
        { env: await this.identityEnv(cwd) },
      );
      if (!(source.trustIdenticalTree && plan.identical)) {
        const gate = await checkMergedUpdate(cwd, to, this.options.updateScratchDir);
        if (!gate.ok) {
          return await this.dispatchMerge(cwd, source, source.brief(plan, head, gate.output));
        }
      }
    }
    // No line in the chat for this: it applied while the user watched the
    // button, exactly like a fast-forward.
    await git(cwd, ["merge", "--ff-only", to]);
    await source.settle?.(to);
    await this.swapIn(cwd, head, to);
  }