Add squash-merge command with conflict resolution

src/cli.ts

@@ -10,6 +10,7 @@ import { action as reviewAction } from "./commands/review.ts"
 import { action as shellAction } from "./commands/shell.ts"
 import { action as closeAction } from "./commands/close.ts"
 import { action as mergeAction } from "./commands/merge.ts"
+import { action as squashAction } from "./commands/squash.ts"
 import { action as rebaseAction } from "./commands/rebase.ts"
 import { action as saveAction } from "./commands/save.ts"
 import { action as diffAction } from "./commands/diff.ts"
@@ -97,6 +98,14 @@ program
   .description("Merge a branch into main and close the session")
   .action(mergeAction)
 
+// ── sandlot squash ───────────────────────────────────────────────────
+
+program
+  .command("squash")
+  .argument("<branch>", "branch name")
+  .description("Squash-merge a branch into main and close the session")
+  .action(squashAction)
+
 // ── sandlot rebase ───────────────────────────────────────────────────
 
 program

src/commands/squash.ts

@@ -0,0 +1,43 @@
+import * as git from "../git.ts"
+import * as vm from "../vm.ts"
+import * as state from "../state.ts"
+import { spinner } from "../spinner.ts"
+import { die } from "../fmt.ts"
+import { action as closeAction } from "./close.ts"
+import { resolveConflicts } from "./helpers.ts"
+
+export async function action(branch: string) {
+  const root = await git.repoRoot()
+  const session = await state.getSession(root, branch)
+
+  if (session && await git.isDirty(session.worktree)) {
+    die(`Branch "${branch}" has unsaved changes. Run "sandlot save ${branch}" first.`)
+  }
+
+  const conflicts = await git.squashMerge(branch, root)
+
+  if (conflicts.length === 0) {
+    await git.commit(`squash ${branch}`, root)
+    console.log(`✔ Squash-merged ${branch} into current branch`)
+    await closeAction(branch)
+    return
+  }
+
+  // Resolve conflicts with Claude
+  console.log(`◆ Merge conflicts in ${conflicts.length} file(s). Resolving with Claude...`)
+  const spin = spinner("Starting container", branch)
+
+  try {
+    await vm.ensure((msg) => { spin.text = msg })
+    await resolveConflicts(conflicts, root, (file) => { spin.text = `Resolving ${file}` })
+
+    await git.commit(`squash ${branch}`, root)
+    spin.succeed(`Resolved ${conflicts.length} conflict(s) and squash-merged ${branch}`)
+  } catch (err) {
+    spin.fail(String((err as Error).message ?? err))
+    await git.abortMerge(root)
+    process.exit(1)
+  }
+
+  await closeAction(branch)
+}

src/git.ts

@@ -101,6 +101,28 @@ export async function merge(branch: string, cwd: string): Promise<string[]> {
   throw new Error(`Failed to merge branch "${branch}": ${result.stderr.toString().trim()}`)
 }
 
+/** Squash-merge a branch into the current branch. Returns conflicted file paths, or empty array if clean. */
+export async function squashMerge(branch: string, cwd: string): Promise<string[]> {
+  const result = await $`git merge --squash ${branch}`.cwd(cwd).nothrow().quiet()
+  if (result.exitCode === 0) return []
+
+  // Check for unmerged (conflicted) files
+  const unmerged = await $`git diff --name-only --diff-filter=U`.cwd(cwd).nothrow().quiet().text()
+  const files = unmerged.trim().split("\n").filter(Boolean)
+  if (files.length > 0) return files
+
+  // Not a conflict — some other merge failure
+  throw new Error(`Failed to squash-merge branch "${branch}": ${result.stderr.toString().trim()}`)
+}
+
+/** Commit staged changes with a message. */
+export async function commit(message: string, cwd: string): Promise<void> {
+  const result = await $`git commit -m ${message}`.cwd(cwd).nothrow().quiet()
+  if (result.exitCode !== 0) {
+    throw new Error(`Failed to commit: ${result.stderr.toString().trim()}`)
+  }
+}
+
 /** Stage a file. */
 export async function stageFile(file: string, cwd: string): Promise<void> {
   await $`git add ${file}`.cwd(cwd).nothrow().quiet()