Require clean working tree for apply and add --dry-run flag (#99)

- Check git status --porcelain before applying; exit with actionable
  message if uncommitted changes exist
- --dry-run flag shows what would be applied without modifying files
- 4 new tests for dirty tree detection and dry-run behavior

Generated by thinktank Opus (5 agents, all pass, Agent #4 recommended).

Closes #63

Co-authored-by: unknown <that-github-user@github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: 3 people

src/cli.ts

@@ -75,10 +75,12 @@ program
   .description("Apply the recommended (or selected) agent's changes to your repo")
   .option("-a, --agent <number>", "Apply a specific agent's changes instead of the recommended one")
   .option("-p, --preview", "Show the diff without applying")
+  .option("-d, --dry-run", "Show what would be applied without making changes")
   .action(async (opts) => {
     await apply({
       agent: opts.agent ? parseInt(opts.agent, 10) : undefined,
       preview: opts.preview ?? false,
+      dryRun: opts.dryRun ?? false,
     });
   });
 

src/commands/apply.test.ts

@@ -1,5 +1,5 @@
 import assert from "node:assert/strict";
-import { beforeEach, describe, it, mock } from "node:test";
+import { describe, it } from "node:test";
 
 // Test the logic of agent selection without actually running git commands
 describe("apply agent selection logic", () => {
@@ -68,3 +68,34 @@ describe("apply agent selection logic", () => {
     assert.equal(agent.diff, "");
   });
 });
+
+describe("isWorkingTreeClean", () => {
+  it("is exported and callable", async () => {
+    const { isWorkingTreeClean } = await import("./apply.js");
+    assert.equal(typeof isWorkingTreeClean, "function");
+  });
+
+  it("returns a boolean", async () => {
+    const { isWorkingTreeClean } = await import("./apply.js");
+    const result = await isWorkingTreeClean();
+    assert.equal(typeof result, "boolean");
+  });
+});
+
+describe("dry-run flag", () => {
+  it("ApplyOptions accepts dryRun property", async () => {
+    const opts: import("./apply.js").ApplyOptions = {
+      dryRun: true,
+    };
+    assert.equal(opts.dryRun, true);
+  });
+
+  it("dry-run skips dirty-tree check (same as preview)", () => {
+    // The guard in apply() only checks isWorkingTreeClean when
+    // neither preview nor dryRun is set. Verify the logic inline:
+    const preview = false;
+    const dryRun = true;
+    const isPreviewOnly = preview || dryRun;
+    assert.equal(isPreviewOnly, true, "dry-run should be treated as preview-only");
+  });
+});

src/commands/apply.ts

@@ -11,9 +11,32 @@ const exec = promisify(execFile);
 export interface ApplyOptions {
   agent?: number;
   preview?: boolean;
+  dryRun?: boolean;
+}
+
+export async function isWorkingTreeClean(): Promise<boolean> {
+  const repoRoot = await getRepoRoot();
+  const { stdout } = await exec("git", ["status", "--porcelain"], { cwd: repoRoot });
+  return stdout.trim() === "";
 }
 
 export async function apply(opts: ApplyOptions): Promise<void> {
+  // Check for clean working tree before applying
+  const isPreviewOnly = opts.preview || opts.dryRun;
+  if (!isPreviewOnly) {
+    const clean = await isWorkingTreeClean();
+    if (!clean) {
+      console.error("  Your working tree has uncommitted changes.");
+      console.error("  Please commit or stash them before running `thinktank apply`.");
+      console.error();
+      console.error("  Quick fix:");
+      console.error("    git stash        # stash changes temporarily");
+      console.error("    thinktank apply  # apply agent changes");
+      console.error("    git stash pop    # restore your changes");
+      process.exit(1);
+    }
+  }
+
   // Load latest result
   let result: EnsembleResult;
   try {
@@ -43,10 +66,11 @@ export async function apply(opts: ApplyOptions): Promise<void> {
     process.exit(1);
   }
 
-  // Preview mode: show diff and exit
-  if (opts.preview) {
+  // Preview / dry-run mode: show diff and exit
+  if (opts.preview || opts.dryRun) {
+    const label = opts.dryRun ? "Dry run" : "Preview";
     console.log();
-    console.log(pc.bold(`  Agent #${agentId} diff:`));
+    console.log(pc.bold(`  ${label} — Agent #${agentId} diff:`));
     console.log(pc.dim("  " + "─".repeat(58)));
     console.log();
     for (const line of agent.diff.split("\n")) {